No matter what system you use - you're going to struggle having some rads with eTRVs and not (In different zones). Whenever there is a demand on a TRV on a rad, any rads within that zone that don't have eTRVs on will heat. The zone valves don't make the slightest bit of difference tbh.
You'd need to do one zone fully with eTRVs or not. Drayton won't be any different.
You'd need to do one zone fully with eTRVs or not. Drayton won't be any different.