Million dollar question...
What would be a reasonable amount to expect to pay for swapping out my existing combi for a new one in the same place?
The GlowWorm 25 quote was around £1600. From what I can see that model is around £800 (inc VAT) - so I assume installation is going to be making up the other £800?
And why not? If he does a good job and instal is done like it should be, then do not see you as being ripped off
Went to a house yesterday to service boiler and fire. Fire had to be reinstalled as it was badly fitted and not installed as per MIs. Boiler also fitted but with undersized gas line and several other defects ( will need revisit to remedy)
If your boiler is fitted using good materials and skills and installer will attend if there is a boiler or workmanship issue without quibble, then what he charges will be fair