I run a little industrial estate and electricity/ tenant churn is an absolute nightmare to deal with. It makes little difference to me whether three phase or single, but all hardware connected with a three phase is vastly more expensive than regular consumer stuff.
I avoid online brokers as they besiege you with calls and emails. If you sign up with one it can be on an auto renewal basis whereby they move your supplier about and escaping this arrangement takes time, call centres, high pressure salesmen etc etc
A 40 sqm storage unit with three phase annual consumption of below 100 kwh is with Eon. June 2024 tariff:
1 year, standing charge-56p, kwh-65p
A 60 sqm car repair shop with three phase British Gas-Lite January 2024 tariff ...
1 year, standing charge 40p, kwh 26.31p
I had a new single phase supply installed in a 60 sqm office with a new smart meter. Eon Jan
24 economy 7 tariff
1 year, standing charge 30p, day 35.1p, night 25.4p
If you don't have a smart meter the electricity companies hassle you for monthly readings and if you don't supply one they can use wildly high estimated readings. Tariffs may say that you have to have a smart meter installed but in my experience they sometimes never get round to installing them ! There is a massive backlog for new meter installations.
EDF failed to show up to install a smart meter, they also arranged for a single phase fitter to do a three phase supply ..... EDF pay £30 compensation for each event like this.
You may get a better deal if you can get an economy 7 tariff as these seem to have lower standing charges.
Good luck and may the Force be with you