Thermostatic Valves for Radiators

[Soup]

I'm considering installing thermostatically controlled valves on my radiators as I have been told that they are far more efficient and effective.

A couple of questions: -

Has anybody done this and have they noticed a difference in household bills and tempetature levels in the house

My rads are a bit old, would it be worth changing these as well to more effective ones ?

 

[Diyisfun]

Not sure if there was a cost saving, taking into consideration the cost of the t/stats, but I think the comfort level is controllable and well worth it. I have recently moved & fitted them to all but 1 rad in my new property.