This has just been advertised in my Union mag.

http://www.gas-elec.co.uk/reduce-heating-bill.html

Has anyone used one or have a view as to it's effectiveness? They seem
very upfront and clear in their claims but at £156 for a couple of
electronic timers and relays, it's horrendously expensive. If the
principle is right, I might be tempted to build my own version, bringing
it right on topic for DIY.

Andy C