DIY addition of thermostat to central heating in scotland (legal?)?

you could know more than the guy you are goin to end up havin to employ.!! Try talkin to your local council they are very helpfull (well they are in sutherland) ps have just been talkin 2 some freinds not 30 mis prior to seeing your Q and they have had their heating on lowish 24/7 and they thing they are useing less fuell(oil)than letting a timer & thermostat rule the roost?????? SO