Worse case, an ISP will get BT to provide a tail for a leased line into any building, it's all down to how deep your pockets are. ECC (Excess Construction Charges) can run into many thousands of pounds. In a major city there may be other providers with networks.
A PSTN line for ADSL should be available anywhere - find the phone number for a close by building and run that through an availability checker to get a rough idea of speed.