Rear pistons need wound back. Can be done by using large prybar,screwdriver, pliers apparently but i didn't want the hassle and got the correct windback tool http://www.amazon.co.uk/Laser-1314-Caliper-Piston-Re-wind/dp/B002V72SHS/ref=sr_1_1?ie=UTF8&qid=1339964940&sr=8-1
Disc retaining screws strip very easily. You really need an impact driver I would suggest.
http://www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_530655_langId_-1_categoryId_165469
I'm surprised no one else had already mentioned it... Lots of brake cleaner and a wire brush to scrub down the carriers and get rid of the rust and crud that will make your new pads stick. And clean the little metal things on the front carrier too.
If you feel confident, get some red rubber grease and carefully remove the slider pins from the carriers and re-grease them - carefully as in don't tear the rubber boots.
I second the wind back tool, makes the rears so much easier, and can also be used on the front with a little imagination so as to avoid pushing the front pistons back in at an angle. £14 well spent.