Baxi Bermuda 401 pilot light keeps going out?

The pilot light has been going out every few days for the last 2 weeks but now its going out every day & the space between it going out seems to be getting shorter, i have checked this site & several others & i have come to the conclustion that the thermocouple is needing replaced which i am getting done tomorrow by a friend of mine who knows a lot more about gas fires than i do, I would like some other advice as to what could be wrong so i can get these changed at the same time as it seem silly to take the fire apart several times if i can do all the jobs at one time, Also if anyone could let me know what the procedure is for servicing the boiler or were i can download an instruction manual for the bermuda 401 that would be great.

Cheers ...... :-)