combi boiler probs now and then?

When switched on, the fan works for a short while, it doesn't ignite. and the DHW indicator light flashes fast.
however if i leave it switched on it will eventually work.

Any ideas? Also I was told if I repair it myself and needed an engineer to work on it afterwards, or service it, they will refuse to do it. Something to do with the F.. European Rules. Is that correct?