Milton has regular plagues of these, especially from nPower and Scottish Power, so this news may be of interest to villagers. From last Friday (1/10) all energy salesmen from British Gas, EDF Energy, Scottish and Southern, nPower, Eon, and
Scottish Power must follow a code of practice which you can find online
here (Adobe/PDF, 244KB).

Section 7 is the one of particular interest which says:

Sales Agents will:
[…]
7.4.2 voluntarily cease contact with a consumer who clearly indicates that contact is inconvenient, unwelcome or inappropriate
[…]
7.4.3 (b) not call on any premises where there is a message prominently displayed in the form of a visible, clearly worded and unambiguous
notice indicating that a consumer does not wish to receive uninvited doorstep sales callers
7.5 Sales Agents will end the discussion and leave the premises immediately at the consumer’s request.
7.6 A contact number must be left with any consumer, on request.
[…]
7.8 Sales Agents must at all times:
7.8.1 be courteous and professional.
7.8.2 seek to avoid the consumer misunderstanding any information given or
making false assumptions, in particular over potential savings.
7.8.3 avoid the use of high pressure tactics.

7.4.3(b) is the one that immediately leaps out: if you’ve not got a sign at your door saying you don’t wish to receive uninvited doorstep sales callers perhaps now is the time to get one. The Money Saving Expert web site has a page which lots of advice in this area including a “No Cold Callers” (Adobe/PDF, 809KB) sign you can download and print.

The code of practice also goes on to explain how to make a complaint if they don’t do this, and what compensation you can expect if they switch you without your knowledge so if your sign doesn’t work you now know what to do next.