Potterton Boiler fires up for few seconds then dies away

Potterton Boiler fires up for few seconds then dies away. Had same problem last year, but it corrected itself - so loathe to get in engineer I can't afford to fix something minor. Gone through the firing up procedures but no joy. Last time it happened, there was work being done on pipes outside by gas board. They said there was no connection - could debris be in pipe? Could jets/etc bet intermittently blocked? Am strapped for cash please help

Similar thing happened to me some years ago on one of the coldest nights for 20 years. In my case it turned out to be the thermocouple(which tells the boiler that the flame is working) had failed so the boiler kept shutting off the gas valve.The gas engineer I called out knew what it was straight away and fixed it in 10 mins.

I hope it's something simple and cheap Thanks

It's a Potterton Baxi Combi 80e. Last time we had this prob there was work going on outside as there is now. It happened before after gas had been temporarily cut off in street for repairs. Could this have a bearing.

is the pressure OK (warning light on boiler) and what is reading on the pressure gauge underneath. Also does the boiler bang and grumble before the light goes out/fails to stay lit

Thanks for your help - have researched around to get enough info not to have anyone 'cowboy' me - if you know hat I mean. Corgi plumber cme yesterday - £25 - call out. Says gas valve needs replacing - which I thought it might be as pilot is on but boiler fails to fire up properly. He was looking at it for ages. Can't get part til Thur or Fri - bill will be £165 - ish. Is that reasonable? Am trying to get the guy to throw in a saftey check and certificate - as I need to let the flat - long story - had buyer but problems with freeholder trying to make me pay £11,500 for repairs (which included stuff he'd agreed to at no charge to me when I bought my lease, internal repairs and decoration to flats he owns etc)means sale fell through and I have to let it till I sort bill probs.

Not clear which boiler it is. Is pressure guage underneath or on the front?

Doesn't sound expensive either way.