I have bought a home and in winter the extremities of the ground floor are very cold. The original part of the building is the centre, and it has been extended in the front and the back. The main living areas are the open plan kitchen (which is the rear extension) and the lounge (which is the front extension). The boiler is in the loft, so when the heating comes on the upstairs radiators heat up first and then the downstairs radiators in the middle of the house. Lastly the radiators in the lounge and kitchen come on. They don't heat up as well as the others unless I turn as many of them off as possible. When the weather is very windy then there are lots of drafts.
I want to improve the situation, but I suspect it is a combination of my boiler not being 'man' enough to heat all the radiators, not enough radiators in some key areas, and unsatisfactory insulation. So I am looking for a tradesman who can advise me on what is required. However, I am not sure what type of tradesman I need. I fear that if I get a plumber in it will be diagnosed as a plumbing issue and if I get a builder in it will be a different conclusion.
So is there a type of tradesman who specialises in the broad subject? If yes what are they called and how do I find one.
If it is relevant I am in the UK.