paulsmithmk wrote:.....You have to wind back the pistons - they are different on each way so either get a commercial RH and LH tool - about £90 or you can get a small tool I think known as a cube £10 that you then use a ratchet form your socket set. I did offside with RH tool before I found out nearside was Left Handed

I didnt have to adjust handbrake but pistons had to go all the way back.
Or you can save a few quid by not buying anything, and using a couple of spanners which you probably already have......
.....with the calipers still attached to the car, remove the handbrake lever from the rear (noting which way it fits!) by undoing the 17mm (If I remember the size corectly!) retaining nut - this will leave the square 'pin' sticking out the inner side of the caliper.....
....turn the pin with a 13mm(??) spanner to wind the piston backwards (one goes left, the other right, depending which side you're working on

) - it will be obvious which way you need to go, as one way will lock the disc up, and the other will increase the gap between pad and disc!!!!
You may need to assist the piston to retract into the caliper with gentle (hand) pressure and a flat screwdriver, but it will go easily.....
...once it is fully retracted, remove the caliper, clean/regrease the sliders, fit new pads, re-install caliper....
....now for the technical bit - adjust the piston position with the caliper just held in the correct place (1 loosish bolt is what i do) by turning the pin the other way with the spanner until it just grips the disc.
refit the handbrake lever (it will only fit in one of 4 positions due to the square hole!) and check that the movement of the lever over it's normal travel will activate the handbrake fully.
If it doesnt, remove the lever, turn the pin a bit and try again - simples!
I often find that to get a really good handbrake, it is necessary to turn the pin more than it will allow you to with the caliper fitted (it retracts a bit when you let go) - just remove the loose bolt, lift the caliper off the disc, turn the pin a quater turn, slide the caliper back over the disc and refit the lever - job done (or at least, it is once you try a few times, then re-tighten the retaining nut and bolt up the caliper mounting bolts).
The caliper will now (theoretically) self-adjust in use, but i still set mine up each year this way, and if you are fitting new pads, you may notice that after a short time, they need to be adjusted a tad as the pads bed in.
One word of warning (and the reason I retract the pistons with the caliper still in situ, not hanging loose under the wheel arch), the square pin is joined to the inside bits of the piston adjustment gubbins, and is in a 'wet' environment with the brake fluid - as such, there is a rubber 'O' ring as part of the mechanism which keeps the fluid inside the caliper at the base of the pin - should you turn the pin to retract the piston without applying a gentle push to the piston (or brake pad!), Newtons Laws of Physics kick in (equal and opposite reaction) and the caliper will decide that it would rather keep the piston where it is and allow the adjuster to go the other way (into the caliper), which may unseat the 'O' ring and fluid will leak out - usually you only see the fluid when its all gone so far into the caliper that you can't actually turn it, so it isn't often a problem, but better to avoid any chance of air getting into the system, and fluid omto the pads! (and having to fish around with some snipe-nosed pliers to pull it back again, by which time the internal springs will have unwound and you need to strip the whole thing apart to re-fit it - been there, done that!).
It sounds far more complicated than it actually is - should take about half an hour a side from start to finish (including jacking up, removing wheel) if no bolts are seized - or possibly a lot more if the sliders are stuck - but even then, it should all be do-able in half a day.
This doesn't incude the procedure for adjusting the handbrake cable (under the central armrest), as it is far better to set the calipers up properly to start with (by disconecting the handbrake cables), then simply setting the cable tension at the end to give the correct number of 'clicks' (3 should grip the disc enough to hold the wheel against hand rotation, and 5 to hold it on a hill)