Hi!
My boiler was cutting out after 1-3 minutes, but pump circulates and
rads get warm until then. The pilot was stable with a blue flame and
the usual lighting sequence was as normal.

I need a new bundi tube from control valve to pilot. This got broken
when an engineer started to check the appliance Where can I get this
and/or do I need to buy the whole pilot assembly?

The plumber's view was was that the gas control valve was faulty, but
other people suggest that gc valves either work - or don't and don't
cut out after time? The guy was unable to continue with testing after
cleaning pilot because the tube ruptured. The valve is a Gemseal
controls version. Others have suggested that I replace the
thermocouple before I do anything else...if i can get a new tube!

I could do with a new burner. Are all these parts available and if so,
where from?

Thanks for any help that might be available. I'm too brassic to get a
new boiler!