Area? What do you mean?
It's in black & white, as you requested, that the £30 Connection Offer is subject to an 18-month contract. Similarly all BT's Calling Plans & Bundles are subject to Minimum Terms
for new customers (perhaps that's what you mean by "areas"?).
Of course, like any negotiation, BT sales staff will have the leeway to offer less onerous terms in individual cases, but that's the exception rather than the rule.
Also
existing customers, once they have expired the Minimum Term, will be able to revert to "rolling 1 month" contracts (even those who were on renewable contracts are able to opt-out, before any one brings that irrelevance in to cloud the issue).
1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU BB => 2010: Orange 16 Meg LLU BB