I've bought some more bulbs and for some reason all is fine. No idea why really as i had previously tried several bulbs.
Thanks Rob for you answer.
The other idi*t who said he has an idea - get an electrician in - you are a je*k. Apart from the fact that the other lights I have installed over the years, just by chance, haven't managed to burn my house down this forum is for advice not for pr*t's like you.
Gary
November 2008