Is the boiler fan anything at all to do with the Heat Exchanger or Expansion Vessel?

I’m about to book a fixed price repair and the only exclusions are theHeat Exchanger and Expansion Vessel.

The fan tries moving but siezes/stops.

Quite certain it isn’t ! I think the other two would require a drain down to replace ! Not a boiler expert though !

No.
Heat exchanger is the big bit in the middle of the boiler, if that fails, then it is not really cost effective to replace.
The pressure vessels do wear out/ puncture, but rather than fitting a new internal one, it is dead easy to fit one externally, but some people (BG) dont want to do that., even though it is the simplest and cheapest solution.

If the HEX had failed, you’d be leaking water everywhere. The expansion vessel is quite a common failure so that’s probably why they have excluded that.
Have you tried rotating the fan impeller (with a pen or screwdriver) whilst it’s enabled?
I think the fan is likely to be to induce/force air into the combustion chamber, but I’m basing that on commercial boiler burner function.
I’m not a boiler engineer BTW!

On firing up it spins briefly making a noise then stops then slowly turns. Stops. Repeat. I tried freeing it up but it just turns at a snail’s pace. I could have a go replacing it as it looks plug n play but I value my neighbours and my families lives to take that risk.

Yeah, best bet. Get a pro in. Could be the safety circuit stopping the fan AND dropping a valve and other stuff that I clearly don’t know about.

Fan bearings can fail. I replaced mine with some from ebay.

typical sticky fan.. bg do fixed price repairs typically 179 should get your fan replaced .. witch is great value as my baxi solo fan is 220 alone..i used bg fixed price repairs alot last year for my tenanted properties.. why would i pay 200 quid plus an hour of my time plus travelling to fit something when they
ll do it and warranty for 179?