After touch/pressure sensitivity not working on WD-1

[Talkingdrum]

I bought an original WD-1 sometime ago off ebay and a couple of the presets made no sound (monsoon and beast). I think I have discovered the reason and that is that those sounds only respond to pressure on the head which has led me to the discovery that my WD-1 does not respond to pressure on any of the presets.
Not being particularly technically minded I assume there is some sort of sensor who's job it is to detect pressure that is not working. Does anybody know anyone (in the UK) who might be able to repair it or is it possible to do it myself? Which part do I need etc?