Please help my Potterton Kingfisher Boiler keeps Clicking?

Hi, Im a complete novice & writing as my husband is away at the moment so need some advice please.
My Boiler did not come on this morning & was making a clicking noise followed by an electrical grinding noise.
I noticed that the light wasnt on so I followed the instructions on here to re-light the pilot light & it lit up fine.
Now the boiler will stay on for a handful of minutes then it tries to relight (even though its on) & makes the horrible clicking/grinding noise.
It is an old Boiler (Im not sure exactly what make it is, just know its Potterton Kingfisher from the case). We had problems with it last year, but I didnt take enough notice of what was going on to know what was replaced.
Does anyone have any clue what it could be as I will probably have to get someone out to mend it & dont want to get done over.
Many Thanks