Hi there, welcome to the forum - great name, used to be my MSN name back when I used to post on the Turbo Nutters forum
When you changed the rear pads, you would have wound the pistons back in (clockwise)? Generally I find this is easiest if you slacken the handbrake cable right off first. Then, I wind the pistons in, assemble the calipers and pads, operate the footbrake a few dozen times, and finally retighten the handbrake cable. This results in a great handbrake - for me, at least.
Assuming that you got the pistons wound in OK, presumably if you now slacken the cable, operate the footbrake, and retighten the cable, things will be better.