Once, I was heading south on the M1 around 4am, I was a couple of miles away from jct 36 when I noticed red lights on the opposite carraigeway and thought “theres summat wrong here” ( I’m bright like that ) I slowed to see what the problem was, all I could see was a car on the hard shoulder facing the wrong way with only one sidelight still working, the front end was smashed in and steam was coming from the front end, the car was at an angle slightly so the rear end was only just inside the white line, I rang 999 and exited at 36 and headed north to stick the truck on the hard shoulder for protection. I was still on the phone to the operator and she asked me to go and look and give her any details I was a little nervous walking towards the car not knowing what to expect, luckily it was just one guy, unhurt but very shocked, I got him to the other side of the barrier and had to keep stopping him falling over as his legs weren’t his best friends, I waited for the ambulance then had to explain that I wasnt involved in his accident before I could go. There were no other vehicles involved and he had driven from London without stopping so maybe tiredness was a factor 
A few times.
Most memorable was finding a small child cycling along the M4 near Port Talbot on xmas day 1999. I stayed behind the cyclist with hazards on until the police got there.
In 1998 I was driving along the A342 Between Devizes and Chippenham late one foggy evening. I thought I saw a parked wagon on the side of the road. Lifted off the throttle, saw it was a sign, then powered back. Got to the junction with the A3102 towards Calne and in the fog I could see headlamp beams moving pretty fast. I said to my passenger about it, just as it shot across the junction missing me by the thickness of a ■■■ paper, and into the fence/hedge opposite, launched over the hedge and ended up on the old road the other side. I ran to look as my passenger phoned 999. It was a Mazda 626. one of the scaffold fence poles had gone through the front, through the engine, through the centre console, and into the back seat. Luckily, it missed both driver and passenger.
Scary thing was, my passenger pointed out that if I hadn’t lifted off due to thinking the sign was a wagon, it would of hit me right in the drivers door.
One busy Friday afternoon in the summer of 2005, I’m on the M40, sat in the lane 1 traffic to join the A34. A BMW shoots past in lane 3 and disappears behind a wagon in lane 2. I then hear a squeal, a bang. Another bang then see the BMW fly over a car in front of me with its roof towards me, then lands on the verge on it’s roof. I phoned 999, and by then loads of people had got out to see to them. So I didn’t stop.
Last one I can think of, was a Transit crashing in front of me, spewing it’s load of coke bottles all over the carriageway, on the M4 near reading. Was 18th May 2005. I know this, as I was rushing from Slough to PMH in Swindon after getting a call telling me my (now ex) wife had gone into labour. (I got funny looks parking my motor in the bus stop at the hospital.)
3 times , twice for cars that I’d witnessed overturning right in front of me ( and I was parked up on one of those occasions!! )
and once , just before last xmas … for me 
I hit black ice on my mountain bike , on my way to work , and broke my leg in 4 places . Still on the sick now , I’m sure Spanky will be along at some point to extract the preverbial !!
Despite ( in the past 27 years ) responding to 999 calls
I have had cause to ring 999 for ambulance
The first thing to say is you first get through to a BT operator who could be located anywhere in the UK So No local knowledge etc
Secondly each emergency service have their own protocols when dealing with a call and in my experience they don’t listen to what is said until they have filled in the box one at a time so for example if you say I need an ambulance for an 80 year old female who is unconcious but breathing blah blah they will take you through a check list and so ignore what you just said
If you live in a rural location you will quite likely get a fire engine turn up who unless you have a conflagration are not much use apart fron the defib oxygen and a pulse oximeter or a do gooder in a car so better than nowt but not much without drugs and proper training but hey they help to meet the targets
Steps down from soap box
2 Times (so far) ,
1st time ,
There was a car parked on the outside lane with no lights or hazards on at 4am and was pitch black.Phoned 999 snotty woman says we don’t deal with break downs ! Took a few mins to explain it was in lane 3 and someone will smash into it if not quick,
2nd time ,
There was a nutter walking across the Kingston bridge , he was in between the carriage ways (ie in lane 3 either side)
I just remembered there was a 3rd time,
Motorcycle rider came off his bike into stationary traffic , was ok I think ambulance and police for that one
came upon a car down the embankment where the A180 joins the m18 n/b a car had just stopped and someone was calling the police, went down the embankment to see if i could help and the driver was out of the upside down car with no more that a bump on his head, the other car driver had helped him out…
back in 99 i was serving in kosovo at a weapons containment site. around 6am there was a hell of a bang outside, a few of us ran out down the road to see a lada(or yugo) wrapped around a tree both people in a bad way, we called up for our MO to come out but by the time he got there the passenger had died on me…the driver was stinking of alcohol… 
On the Vauxhall trunk to Gloucester, running down the A40 around Burford when I spot a fast moving source of light coming left to right. ■■■■ me i though, he’s going at a pace. ■■■■ me again I thought as he came flying out of the B4425 and into the ditch the other side. (Google maps is my friend, Im not sad enough to remember B roads as well.)
I pulls over and hits the hazards, phones the old bill and the ambulance while running over to make sure said loony is alright. He is nose down in the ditch, back wheels off the ground and wandering around on the verge. No signs of bleeding so I ask if he is alright. He says he is fine, asks if I can give him a push out of the ditch!
Youre avin a bubble my son, I replied, to a bloke that was at least five years older than me! You need a wrecker with a winch to get that out, and it wont be drivable. While the police are on their way he says he must have aquaplaned off.
Thats funny I thought, given the fact that the road is bone dry, but hey. He told me to get lost, effectively, so I took the hint on the third try and got on my way. Used the handsfree to phone 101 and update the boys with blues. Waved at the police as they came past me going the other way.
The only other time I have called the police was a 101 rather than a 999. That was for a foriegn truck, could have been a Romspedition but i forget now, reversing up the on ramp for the M1 south at J15. Scared the ■■■■ out of me, I was running at 43t so it was very lucky I missed him.
A few times but most notably just before Christmas. I was running in on a Saturday morning near Stafford (M6) when I saw a broken down car with the occupants, one being a baby in mothers arms. I called 999 & asked them if they despatch HATO in which they said they’d despatch HATO right away.
phoned the rozzers when i saw some traveling folk nicking diesel from trucks on newport pagnall,cops arrived and caught them red handed,result, but a police officer phoned me later that night and told me they had only been given a caution because they hadn’t nicked any diesel, only ‘came equipped’.
Fair play to you , I’ve only dialled once as a transit tipper overtook me on the motorway greedy boards up the side full off rubbish and no net after getting a kitchen door fly into my windscreen I thought is this bloke for real I phoned as a traffic car went flying by someone obv got there before me I’ve helped many people if I could over the years worse was an elderly man at a set off lights on a hill, every time they changed green he wouldn’t move every one behind me thought it was me and the beeping starts I jumped out to see if the old chap was ok he was fine but had totally burnt his clutch out on many attempts to pull off, what sticks in my mind is there all behind me tooting there horns yet no one offered a push and all sat there watching me push a micra up hill on my own there are some t@#ts about!
Had to call the old bill last year as the van I was following was weaving all over the road. It was on the A16 from Boston to Spalding and they crossed into the flow of oncoming traffic at least half a dozen times. Don’t know the outcome as they started doing some crazy overtaking but no Police came past me. I hope they didn’t get away with it.
shade:
3 times , twice for cars that I’d witnessed overturning right in front of me ( and I was parked up on one of those occasions!! )and once , just before last xmas … for me
I hit black ice on my mountain bike , on my way to work , and broke my leg in 4 places . Still on the sick now , I’m sure Spanky will be along at some point to extract the preverbial !!
Blimey! How fast were you peddling to break your leg in 4 places? 