Usual way is to put the roomstat in an area where is no TRV, typically the hall. And if necessary throttle that rad down so that the TRVs do something before the roomstat is satisfied. Roomstat in the hall is common, but IMO it would be more logical to put it where you spend most time and are most concerned about comfort, usually the living room or lounge (etc, depending where you're from.)Going back to my query, if the roomstat was set higher than the TRVs cutting demand, then the cycling would still continue as the system (pipe) cools below SP-5(say). The only way to totally stop my (simplistic) boiler cycling would be when the roomstat cuts out, and being a switch in series with the timer, cuts the power.
"And if TRVs and cycling could run the heating demand, it doesn't feel like the roomstat makes much of a fuel saving." If there were no roomstat the boiler would cycle on its controlstat the whole time CH was called on the timer. That can't be economical.