Hmm - I should have thought more when I made my previous post - I just jumped to a conclusion.
As Cds has suggested with his questions, we need some more information.
Does the burner go through part of the firing sequence before locking out? If so, how long is it until it locks out? A minute or two which means it's running for a while then stopping? Or up to a minute then stopping? If the latter, how many seconds is it until it locks out? Or does it lock out as soon as the call for heating/hot water is given?
Does the boiler lock out every single morning? This could be a programmer issue where the clock is faulty after it changes to a new day.
Re the timing above, if you're in bed when all this happens you need to get up earlier or set the clock for later so you can wait beside the boiler to establish what is or isn't happening and when.
Sorry to sound negative but there are so many possibilities so the more information you can give the more likely you'll get an accurate answer.
