ServoWarm Elite Pilot Problem H E L P !

[spliffy]

Hi,
My old Servowarm Elite 30 boiler was working fine until I switched off the gas. After switching on again, I went throught the procedure of holding the button in for 10 seconds after striking the flame, but the pilot would not stay on. Suspecting the thermocouple, I changed it, but am still having the same problem.
Is it possible that the reset switch needs changing ?..if so, where can i get one??? or could it be the thermo-electric valve ?????
H E L P !!!
Also, does anyone know the best place to buy parts from.
Thanks in advance !