It seems similar to what I found when I bought this house, some one thought it seems you could split the house into two zones by using two pumps, that's what had been tried here, flat and main house, one pump for each, unfortunately it did not work, which ever pump ran, it would push water around the other zone backwards, so I had to get plumbers to fit zone valves.
In fact mine was worst than yours, as it seems some one had tried to fix it, and the fix was three independent FCU's and a pump on a 13A plug and socket.
Likely there is no way of having central heating without domestic hot water, if the boiler is running you have domestic hot water, however it is likely wired so you can have domestic hot water (DHW) without central heating (CH) the idea is if pump does not run, then no CH, however this is a bit hit and miss, once the CH is warm thermo syphon will likely keep it running at least upstairs, the plumber and oil heating engineer I got in scratched their heads and hadn't a clue, I did not care, I designed the wiring from scratch.
However plumbing is not perfect in my case, as no by-pass valves. The pumps you have seem quite modern even if an old boiler, I don't know enough about those pumps to help, however I can say what happened to me.
Although I fitted to motorised valves, in hind sight I could have got away without it, I also fitted new thermostatic radiator valve bases, and electronic heads on them all, and they do shut off fully, so that would stop thermo syphon, what I don't know, is what the pumps will do if all TRV's close, will they be damaged, may be some one else can answer that? So with a wall thermostat and a TRV head running same schedule placed in the same room it all could work as it is?
My pumps are on the return, so could not fit by-pass so I was told, your pumps may not need a by-pass either, I don't know, but with lock down it will be hard to find some one with the skill to fix it, so if you have TRV already fitted, easy way may be £10 electronic heads so you can program each room, big question which I can't answer is would you need by pass valves.