I've bought a replacement plip from Peugeot and the guy at the parts counter told me that you can swap the transponder elements over so there's no need to get the keys recoded. Sure enough, wedged into the fatter half of the fob, next to the blade, is a small black oblong "thingy" which is the transponder element. I swapped these over and the new fob starts my car 8)
Only thing is, I can't seem to get the fob to operate the remote central locking. I've tried various combinations of key-in-ignition-button-pressing but to no avail. Does anyone know the correct sequence, or even if it is possible without dealer intervention (at a cost of £50?)