Interesting that you managed to get water and mains electricity connected, presumably they provide a bill for these services and those bills have an address , what address is on the bill , something like ‘patch of ground outside of *****’ ? and with domestic water supply, unless on a water meter , the bill is based on an arbitrary old style rateable value , so in areas that predated water meters , so housing built until the 2000’s , and haven’t chosen individually to get a water meter installed, a 3 bed house pays less in water charges than a 4 bed , because of that implied rateable value , even if the 3 bed actually uses more , on what is your water bill based ?.
As already stated , a business ‘order’ is probably the only way to proceed, domestic supply relies on the ISP identifying your registered address , from an Openreach postal address file , which is closely based on the Royal Mail dataset , to be on that database as a residential dwelling, certain criteria apply, being registered for council tax, have a front door and a letter box are some of these qualifying criteria.
Business don’t necessarily need the same criteria ( and presumably use a different ordering portal ) for example consider a road construction or road maintenance scheme with temporary portacabins erected along the roadside for the duration of the works , these cabins don’t have a postal address as such , but can order a business service, but are not a standard install , liable to a paid for Openreach survey , and any additional work to enable supply is also paid for by the client ( like extra telegraph poles etc. ) at a minimum, even if existing line plant is in the vicinity as potentially in your case , a survey officer needs to identify it , as obviously there is no registered address that has already been pre-matched to existing infrastructure as with a regular domestic order.
I wouldn’t expect to get regular pricing with a range of providers available , it’s going to be much more bespoke and expensive , using a business type provider ( not necessarily a leased line ) with pricing commensurate with that type of business ‘line’ .
