Regulations

Its easy to do.

NT

This is a newsgroup, despite what diybanter would have you believe.

Dave

Yes central heating controls are notifiable under part P.

In practice it's most unlikely there would be any repercussions to simply ignoring the regs and DIY-ing it (assuming you wire it up safely and correctly), unlike say replacing a CU or rewiring a house which might attract attention and awkward questions when you came to sell.

As to the type of stat you might consider a programmable thermostat which lets you vary the temperature at different times of day and days of week e.g. warmer in evening than daytime, cool but not off if it gets really cold in the night. The Honeywell CM907s (at about £45 from Heating Controls Online) are the user-friendliest I've found, although the larger Horstmann one from Screwfix is not bad for about £30. Honeywell also do wireless versions of the CM907 for about £90-100 which allow you to position the sensor/control box in the best place regardless of cable runs. They also do 1-day versions of the CM907s called CM901s and screwfix do the wired version of this for about £43.

The Hosrtmann wireless for about £70 form screwfix is a good unit and can save a lot of wiring.

A programmable room stat would be a good choice. It will take the place not only of a stat, but does the job of timer as well.

Part L would probably require that a stat be fitted should the boiler get replaced... Not sure if there is an impact on an existing install

It probably is notifiable under part P. However this is one of those cases where "doing the right thing" (i.e. paying a building notice fee etc) will make a very significant addition to the cost (i.e. more than the cost of the stat), and will bring no dicernable benefit to anyone that I can see.