What if the loads I mentioned were specified and you 'had' to install them. Would you keep a single phase 100A supply or suggest an upgrade to 3 phase?

I'd probably want more information (sorry!) - what's the building heat loss likely to be? (i.e. how much will the heating draw long term) - what's the cost of an upgrade to 3-phase? (unless you already have a 3-phase head and it's just a matter of upgrading the metering, it can get eye-watering expensive quite quickly, as DNO's tend to ask for the actual costs if doing things these days - unlike the old electricity board days, they can't subsidise connections on the basis of future income from your bill). How much room for expansion would you like? (e.g. EV charge point). How acceptable would load-shedding be? (common practice in France, where you'd be expected to manage on a 45A single phase supply). I think I'd look at a supply upgrade as a last resort.

   - Andy.

AJJewsbury said:

it can get eye-watering expensive quite quickly

I paid about £1500 for a completely new supply including digging up the road. I don't think that 3-phase was much more expensive than single. Of course if the service cable needs to be replaced, that is going to make an upgrade rather costly.

Ok thanks for the advice.

Ok thanks for the advice.