Heating, Thermostats and TRVs

I was fitting some heating controls last night and wondered about the best position for a room thermostat so did a little web search and found some big argument about whether a room thermostat (RT) is a good idea or not. Interestingly the Building Regs say you need one (or probably need one?) to comply with Part L (conservation of fuel and power) so you don't really get to decide if you want a legal house! Anyway, I dug a bit deeper and it is a good example of 'flawless' logic meets the big bad government when in reality the logic is flawed.
Most people were saying something like, 'how can a single RT add anything to heat sensors (TRVs) effectively in each room?'. Although someone suggested that TRVs are not very well positioned or accurate etc. it was correct that they could always be turned up to a suitable number which might be higher in one room for the same temperature as another. It was worrying that apparently even some plumbers are ignorant of the purposes of the RT and would appear to be suggesting not bothering until fortunately, someone who actually knew what they were talking about appeared on the forum.
The reason you need a RT is for the following situation. What happens when all your rooms are warm enough and the TRVs all close? You will either have a single radiator with no TRV as a bypass or a pressure operated bypass valve which allows the water to go somewhere when no radiators are open. So for a period of time, which in the warmer spring/autumn months would be longest, the boiler is STILL heating water and this is going round a certain amount of pipe losing its heat for no reason and not giving the boiler a rest. When the temperature of the water drops too much, it will fire up again and simply waste gas. The RT job is to literally switch the boiler off when the whole house is up to temperature so that zero gas is used until the house gets cooler. This of course begs the question of where to put it.
Do NOT put it in a room that always gets warm because of sunlight or because the radiator is turned up high (bathroom, kitchen). Do NOT put it in the lounge if either you have the lounge turned up high or you have another source of heat in the room (open fire etc) that would otherwise switch the thermostat off and let the rest of the house get cold. Do NOT put it somewhere that is often cold such as a back lobby or near the door of an entrance hall which might never get warm enough to switch the thermostat off. My own suggestion is to use the lounge if you do not have any alternative heat sources or otherwise the upstairs landing which is a reasonable indication of the overall heat of the house. You can set the temperature slightly higher (a couple of degrees) than you would otherwise have it for that area to ensure that the rest of the house gets enough time to heat up. If you find that it works perfectly while some rooms never get warm, you will need to balance up the system. Ideally, the rooms should all warm up at the same rate although some will switch off earlier than others. If when you turn the heating on, one radiator or room gets noticeabley hotter quicker than the others, turn down the 'close down' valve (the one on the other end to the TRV) by about 1/2 a turn. If a rad never seems to get warm or as hot as the others, open its valve up by 1/2 a turn. Over a few days, you should notice a much more even heating up.