We’ve recently installed a smart TRV system (Drayton Wiser). It seems pretty good, and a really easy install if you already have thermostatic radiator valves. It essentially converts a simple, single zone, central heating system, into as many independent zones as you care to buy smart valves for, each running their own temperature schedules.
So, I think we can say we’re now heating individual rooms. The bedroom warms up in the morning and evening, home working rooms during the day, and the living room in the evening. I’m sure heat does leak between adjoining rooms, but they still feel cool if you wander into them at the wrong times. I wouldn’t like to say how much we’re saving, as we installed it just before the cold snap before Christmas, and burned a lot of gas that month anyway. Previously we’d turned things down as much as we could bear. I think we’re more comfortable now, but it’s a bit too early to say if we’re really using less gas to achieve that.