Cheers Andy.
Tonight I had a break from thinking and stripped down the two front brake calipers as the donors brakes were quite frankly non existent, and boy was I right too the pitting to the pistons is really quite bad I will need to replace the pistons. I know a place that will acid dip and plate the calipers and carriers for free and then I'll rebuild them. It'll be a lot cheaper than replacements. Not sure if I'm brave enough to do the rears they look a little more involved.