Likely yes, but it is not that easy or straight forward. We have ring finals, radials, and spurs, and the supply can be from a 16 to 32 amp supply in the fuse board or consumer unit, also one can have lower amp supplies for special installations. In the main we use fuse connection units (FCU) to supply boilers, mainly so it can't be unplugged.
Personally I think using plug and socket it good, as one can then easy power central heating from a generator in an emergency, however many boilers state in their installation manual that they should be supplied from a FCU and many plumbers insist this is done. Also some even require that the supply is RCD protected with a type A RCD, why I have not a clue, my central heating is the only circuit in the house which is not RCD protected and as a result has to be a FCU.
This chart
shows generally what is permitted. As to who can fit what, it depends where you live and what room the boiler is in. In Wales where I live wiring in a kitchen needs notifying so often the plumber will not touch it, England, Scotland and Ulster all have different rules. And the laws are not very well written so there is some debate as what can and can't be done.
I don't think many people take any notice of the law, but you ask what you can do. One would hope the person fitting the boiler would have looked at the installation first. Not only the electrics but also the plumbing, a lock shield valve on an old header tank system is unlikely to take the pressure of a modern sealed system. And you may not have TRV's on an old system, so changing things after he has surveyed what is required is likely to cause problems.
What
@Murdochcat says is correct, but a lot depends on how jobs worth the installer is.
