Thanks for all the help guys.
Ye, was going to put a tiny smear of red rubber grease around the piston sides too to help it slip in, most (if not all of it) will be removed by the seals as it slides in but should help it go in nice and square.
I didn't have any problems getting the old seals out, used a very small flat bladed screw driver and very carefully lifted a part of the seal and it was easy to remove them by just holding the seal between the scewdriver and my thumb. Obviously I was very carefull not to damage the edge of the alloy casting where the seal sits.
Both dust seals were well past it. The main fluid seals looked ok but when I took them out the canals they sit in were pretty furred up with stuff so gave it all a good clean out. Pistons came up almost like new, very slight pitting on the pad edge but nothing on the side walls so won't ruin the new seals.
Going to paint the caliper too as it's looking a bit flakey.
Chris