My boiler ran happily for over two years (without servicing...... ahem!) until I got it serviced in August '06. Since about November, it's started to lock out (at the burner control box) mostly when it's set on auto and has been sitting for a while, i.e. during the night. It's situated in my garage and the flue comes out the back of the garage at a low level.
When I reset the button on the burner control box I hear the initial stages powering up, a click from the control box and then it either fires up loudly with a big puffing noise (20% of the time) or it just cuts out again before firing up (80% of the time). It's driving me nuts. When I had it serviced in August I had to get the Danfoss control box in the house replaced because it was having problems with the water and the heating being on simultaneously. No such problems from there now.
Help!

A fair point! I did call him in November and he directed me to the control box on the burner. I reset it and he informed me that I was very lucky never having to reset it before then. I thought that it was getting older (like me) - it's 10 years old now - and I would just have to put up with the occasional lockout. The guy came back this morning and tested the control box - it's fine apparently. He said he didn;t like the sound it made at ignition and is talking about taking away the whole burner to test it and recondition it. Worst case scenario he's talking £400. Is this fair? I see online you can get a whole new boiler for about £1050-£1150.