Hi and welcome.
Sorry I cant help you on this one but I'm sure there will be someone along soon that will help.
I also have a Porsche Boxster 03 plate (986) face lift model. but haven't changed the pads on this car yet.
Talking about pad sensors I remember changing pads on one of my cars long time ago (cant remember what make it was) where when the pad wore down, the disc then made contact with the sensor that was buried in the pad, and completed a circuit and your warning light would come on, this way you just change the pad and put the sensor back into it and wait for the pad to wear down again before making the circuit, no need to renew sensor, Simple

last time I did any brake pads was on my daughters BMW and later on my wife's Mini, (BMW) and lo and behold guess what, these sensors are the other way round, it's only after they have worn down with and at the same time as the pad do they then make a contact and then the warning light comes on, the only difference now is you have to buy new sensors as well as new pads, it sounds as if Porsche have the same system, the trick will be to change the pads just before the sensor wears down, if you can catch it just right, to late in your case, cant remember how much the sensors were but what I do remember is that my Daughters 3 series was the same as my wife's Mini but cost three times as much
Guvs