driver-hire.co.uk/site/index.html
go to drivers regulations and click on tachos 
i hope this is of use to some of you new lads out there.
Thanks for posting the link kitkat.
That gives a good simple explanation of the rules Kitkat, nice one.
Nit picking one small point they say
It is the Driver’s responsibility to ensure that the Tachograph clock is set to correct UK local time before starting any journey.
There are quite a lot of trucks around that while being owned and operated by UK transport firms are in fact registered abroad and the tacho rules say that the clock must be set to the time of the vehicle’s country of registration, so if anybody does work for an agency and finds themself driving a truck that is registered outside the UK the setting theTachograph clock to UK time would be incorrect. A small point but better to do it right than have problems with VOSA in a check.
This is something that often comes up when I get stopped in checks over the water, so much so that I carry a laminated card explaining in several languages that the clock must be set to the time of the country of registration and quoting the actual chapter and article of the regulations, Chapter IV, Article 15, paragraph 3. Doesn’t half put a damper on a Gendarmes day when he is trying to nick me for having the clock set on the wrong time and I produce the laminated card. 
Excellent bit of advice Coffee, thanks for that.
I was out on the monday after the clocks changed and the tacho was still on BST, so I just made a note on the back of my chart. ( I’m an agency driver). On my next job a got the low down on how to change the time. Boy is this game a steep learning curve for newbies. The main thing for old f*rts like me is to learn to ask.
Gordy
Coffeeholic:
That gives a good simple explanation of the rules Kitkat, nice one.Nit picking one small point they say
It is the Driver’s responsibility to ensure that the Tachograph clock is set to correct UK local time before starting any journey.
There are quite a lot of trucks around that while being owned and operated by UK transport firms are in fact registered abroad and the tacho rules say that the clock must be set to the time of the vehicle’s country of registration, so if anybody does work for an agency and finds themself driving a truck that is registered outside the UK the setting theTachograph clock to UK time would be incorrect. A small point but better to do it right than have problems with VOSA in a check.
This is something that often comes up when I get stopped in checks over the water, so much so that I carry a laminated card explaining in several languages that the clock must be set to the time of the country of registration and quoting the actual chapter and article of the regulations, Chapter IV, Article 15, paragraph 3. Doesn’t half put a damper on a Gendarmes day when he is trying to nick me for having the clock set on the wrong time and I produce the laminated card.
the laminated one
neil, it might be a good idea if you could scan it and place it up here so as others could print it of( if readable),that way it might save some one from getting hassle just an idea.
To change the time of the tacho clock is actualy quite simple. It has to be, so that drivers can do it 
.
The ones which are part of the speedo and hinge down, have a flat white plastic toothed wheel (like a penny almost in a slot). Close the tacho/speedo head as much as possible to give you the best view of the clock. Adjust the clock to the correct time by turning the wheel.
If you have an older unit which has two pegs and the central hub, with a locking ring. The locking ring is also the key which fits a peg and adjusts the clock.
Volvos with the tacho which pops up from the back of the dash have a large knurled knob sticking up from the mechanism that the disc is fitted onto.
The new CD type tachos have a variety of different styles, but they should reset themselves between BST and GMT provided that there are no discs fitted in them. Otherwise they need to be adjusted through the vehicle computer system and the tacho clock, at the same time. (Not exactly the same time obviously, but don’t adjust one, drive the truck, then adjust the other).
Also, as far as I know, it is an offence for your clock to be wrong by more than two (2) minutes. I think that you will normally be allowed a bit more lee-way than that though (say 5 mins?)
With mechanical clocks, check to be sure that the clock isn’t 12 hours out. Do that by putting a disc in, leaving it in for a minute or two and pulling it back out. The marks will show what time the cloch is set to. You can also put a disc in and check it against the mark. The marks are not always easy to see though.
The new CD type tachos have a variety of different styles, but they should reset themselves between BST and GMT provided that there are no discs fitted in them. Otherwise they need to be adjusted through the vehicle computer system and the tacho clock, at the same time. (Not exactly the same time obviously, but don’t adjust one, drive the truck, then adjust the other).
i have a 53plate MAN and that has the cd type tach,it does not change itself i have to do it,plus the tacho clock is the same as the clock on the dash.thats how it arrived from the dealers and thats how i keep it.