Yes it'll work; yes it'll satisfy BRs - and in many ways is better than TRVs in that you can have a separate program for every room. When we moved up here in the late 60s, the bungalow at the top of the street had been done like that - stat and motorised valve for every room !
However, where TRVs are better is that they provide modulated flow through the rads - so when the room is "getting up to temperature" the rad output will reduce gradually rather than shutting down. With stats and motorised* valves, the rads will be in on-off mode and room temperature will go up and down a couple of degrees as the system cycles.
Other thoughts ...
I wouldn't have thought it great to run the rads of the same manifold as the UFH - the UFH needs a relatively low temperature so unless you have enormous rads they will under-perform. Also, you could reduce plumbing by going for a "traditional" rad layout and using a thermal-wax actuator on the radiator valve - just like a TRV head but it's got a wax capsule and electric heater element. If someone wanted to go back to "normal" controls, it would be easy to just swap the heads for a thermostatic one (assuming you choose the right valve body).
Have you considered something like ZigBee or Z-Wave (one of them is one-way, the other allows two-way communication IIRC) ? You can get replacement TRV heads with radio control in them - so they could be re-programmed by the system controller as required to provide as complex a daily temperature profile as needed, while retaining the proportional control of TRVs.
Whether I'll find the time is another matter, but I had in mind taking feedback from the heads and altering the flow temperature to suit (ie as the heads throttle back lower the flow temperature**) either by weather comp on the boiler, or a motorised mixing valve off a thermal store if we get round to building the extension (we don't have room for a cylinder at the moment).
* In your proposal, "motorised" includes the thermal-wax actuator head on the manifold.
** My idea was to keep the system with a reasonable flow at all times - thus giving rads which have a fairly uniform temperature rather than a hot spot near the inlet when on low output. Either by monitoring the flow rate, or getting feedback from the TRVs as to their position.
EDIT: If you did go for thermal actuators on the rads or a manifold and room stats, try and find a stat that can be set to little (or no) hysteresis. The wax capsules can take several minutes to operate, so it's easy to get a system that overshoots and oscillates. The less the hysteresis, the less the chance of that - Honeywell told me*** that their heads were completely OK to operate in a pseudo-proportional mode with no limits on how often the supply was switched on & off.
*** At my last job I was involved in the office heating and cooling. The initial aircon controls were mechanical stats on the wall - and with several degrees of hysteresis we really did get problems of the system cycling very uncomfortably. As in :
Stat calls for cooling, during the 2 minutes it takes valve to open the room warms up some more. Cooling kicks in, and it takes a few minutes to bring the room back down to temperature, and then a few minutes more to go down by the hysteresis in the stat. So by the time the stat opens, the wax capsule is "well heated".
Stat finally opens, but valve takes 5-7 minutes to close during which time the cooling is still running. So room over-cools before the cycle starts again.
In some cases, it would even cycle between heating and cooling because the overshoot was that great.
