[Closed] CH boiler help needed please!!

Aaargh, just in time to wreck the weekend - beautiful day outside and the boiler decides not to work!

Its a Ravenheat CSI 85 condensing boiler, when I switch it on, not a great deal happens for 20-30 seconds, then the ignition failure light comes on. Its an electric ignition and I think I've narrowed it down to a problem with the fan. Took the cover off, found the fan and watched as I switched it on, heard the fan motor hum and buzz and watched as the small fan wheel didn't turn. If I try and nudge it with a plastic knife, there's resistance in both directions. I can't see it catching on anything.

With the unit off, the fan spins happily, so I wondered if it was perhaps moving on the shaft when powered and getting stuck. Removed the fan unit and lightly oiled the shaft with silicon oil, reassembled but still the same result. Thinking now it might be the fan motor is unable to spin the fan, the resistance I can feel when its powered is almost like the motor is trying to spin it in both directions.

I think everything else is OK, because I can get it to light by blowing into the rubber tube that supplies air to the fan from the inside of the flue ring, which I figured was me doing the fan's job for it and as soon as I stopped blowing, the flame went out.

Looks to me as though the fan motor is to blame, and reckon my next step is to replace the fan unit (which I'll happily do myself) but this is the first boiler I've opened up and was wondering if someone who knows a bit more than me might be able to give me a couple of pointers?

Any help very gratefully received, cheers!