I spoke to the company I usually get my tyres replaced at, as I wanted to know what the procedure was for replacing valves. I was informed that there plenty of companies/individuals on Ebay that you can get them from but not all of them provide ones calibrated for your individual car. I understand that if you get ones NOT calibrated for the car you have to go to a dealer, at a cost, for the procedure to be carried out.
If you obtain ones calibrated for the car, it is just a case of cycling through the display, where the speedo is displayed, until the tyres symbol is shown press and hold the OK button until the display changes, and away you go.
I have never personally tried this but it sounds feasible, someone like AOne maybe able to advise you better as I think he has more that one set of tyres.