I have just replaced the rear calipers on my new TF. I was going to strip and clean them up like I have done in the past with my other TF's, however I found a set on ebay new for under 90 quid for both sides....not worth the time and effort to refurb the old calipers as both old calipers were well rusted, albeit working fine. I just stripped, derusted and painted the carriers and handbrake cable brackets and fitted new slider pins. I also painted the new calipers with VHT paint.
While they were off, treated the car to some red braided brake hoses too. Recent MOT after fitting the brakes, gave the handbrake a 2% error in balance between both sides!