Looking at the brake pistons it was clear that I would benefit from fitting new ones. Remember that they are the same as Porsche 911 ones (47.97mm x 30 mm) and I bought four new ones and the required seal kit from a company called BiggRed - total cost around £120.You can see the rust removed to reveal shiny casting ready to be reassembled. De-grease the whole thing and plenty of compressed air to make sure there is absolutely no dirt in the callipers.
Fit the new hudraulic seals and pistons with a little brake fluid on the piston as you push it in. I also add some brake grease (red) around the piston as I finally push it down into the calliper housing.The cut-away on the mating face of the piston has to point towards the forward rotation of the brake disc (brake rotor).
Then fit new dust seals and spring clips - these can be a PITA to fit.All rebuilt now and ready to re-install on the car. These callipers could do with a gold repaint really, but they still look ok from through the wheels so I will wait until summer to do this.
After rebuilding both front callipers with new stainless steel pistons and new seals I decided to also fit new discs bought from the BremboShop and of course new pads (same as Alfa Spider).So finally all new brakes and no more pulling to the right :)