I have seen posts about this before but they all seem slightly different so here are my symptoms;
Boiler runs OK but at times throughought the day it seems to cut out. The times I have caught it going out I notice the Fan LED is flashing but usually this stops flashing after a few seconds. The pump is running and after a while the boiler starts up again. There are no other LED's on and it doesn't seem to try and start up and fail at any point. I have noticed more noise than usual from the boiler which sounded like it might be the fan but is difficult to pinpoint.
When it comes to repair I've got the manual and I can replace a fan or PCB but would not be able to check any settings if that was required so would like advice on what repairs are possible for a competant DIY person like me.

MANSELL, November 2008

you need to catch the boiler in the act of making the noise, most likely is fan just but a long screwdriver to it with your ear on the handle and you will hear the noise very clear, if the fan is noisey then its obviously stopping when hot and starting when cool'd down. easy to do no equipment or setting up needed just make sure you get the fan to suit your model

mark the gay boiler man, November 2008