Ideal Elan Boiler - cuts out and pilot light
 

We have a (approx. 16 year old) Ideal Elan boiler. We seem to have an intermittent problem in that the pilot light will go out every now and then. Sometimes it relights straight away using the normal process. Other times it refuses to relight, I give up and come back half an hour later and it then relights straight away. Other times it will relight, I flick the switch so the boiler fires up, then fairly shortly after the whole thing will go out again. On watching the flame when it does stay lit and then fires up, I tend to see a bit of pulsing or turbulence in the main flame then it goes out.
Did think perhaps it coincided with particularly windy days and may be a problem with a draft getting back in, but has happened today and there's not a breath of a breeze!

Any thoughts?