Looks like I’m going to be using the Dartford crossing in the near future. Just hoping to pick a few brains and get some info that isn’t generally on the website. Any info is much appreciated. I’ll be using it late night early morning pulling either 14"10’ or 15"10’ trailers.
Unfortunately, this will be early hours and as such the woolworth fairy won’t be an option.
It’s pretty painless to be honest - going southbound (clockwise), you go over the bridge. There’s no barriers or stopping (except for the traffic, although at the time you’re heading there it should be ok), just crack on and enjoy the view.
Going northbound (anti-clockwise), you use the tunnels. There are two of them, each with two lanes. The left tunnel is restricted to 15’9’’ and the right tunnel is 16’6’‘, so if you’re pulling a 15’10’’ trailer you’ll need to get into lane 3, although this is well signposted.
Make sure you or your boss pays the charge online by midnight the following night, and one other thing to mention - if you’re entering the tunnel crossing from the Erith industrial area (Junction 1a) and you’re over 15’9", follow the diversion to (I think) Junction 1b, as joining from 1a there isn’t enough time to safely get over into lane 3. This has caught quite a few deckers out and it’s 3 points and a fine if you do this!
I usually use it 2-3 times a week, it’s a total non event, just remember the above and enjoy the drive 
You are correct, there is a diversion sign posted for vehicles over 15,9. Rejoin the main drag heading south towards Canterbury. Come to 1b, up and round the roundabout and drop back down, move over to the 3rd lane and you’ll be golden. Make sure you are paying attention though, they take a very dim view of drivers over 15,9 trying to enter the left bore. Its normally 3 points and a fine made worse by the lights, sirens and barriers that come down, you then have to sit and wait till someone comes out to fetch you and drag you back round.
The RIght Bore (16’6") is often closed at night, leaving the 15’9" bore open on it’s own, often with little or no fanfare.
If you join the approach road at J1a - you’ll be committed to the lower tunnel regardless of if the right hand bore is open or not.
The only real solution to this - is to get a lower trailer for night runs that involve the dartford crossing.
Charging Point is the gantry near where the tolls used to be. If you pass this point at 05:59 or earlier - you don’t need to pay.
Many do though, “because they’re not sure where the cutoff lies”… 
Roadworks at night often cause delays of 30 mins+.
Shame the driver of the argos decker hadn’t read this post before tonight. Looks like he had come down the on slip from j1a. Was stopped on the hard shoulder.