Yes there are many benefits of having a new boiler.
I was trying to supply a simple monetary framework on which HCT could base his decision and assuming the GOV efficiency database means what it says. Does it exclude or include hot water production?
It sounds like the start of an interesting discussion on what is meant by efficiency, the components that complete-heat mentions (insulation, heat exchangers) are the very ones that give that efficiency and are in the equation already. I don't think the database includes add ons such as climate controls and specialized control routines etc. These components give the fastest payback e.g.the external thermostat, which allows the boiler (if programmed correctly) to react to outside temperatures and so operate most economically by modulating the burner to get the radiator temperatures just right.
In terms of economics the life expectancy of the boiler is a large consideration in many people's minds, this depends on how it is used and maintained (and here the climatic controls are helpful).
We cannot ignore the cost of servicing and replacement parts. You have to remember that some simple old inefficient boilers with cast iron heat exchangers have been soldiering on for years outliving their new contemporaries who are blowing pcbs at over £100 a time.
Some swings and roundabouts here