Sergio Fernandez said:

The Plant Room/Services room could be used to house some of the following
Boiler Gas/Electric/Hydrogen
CU/DB (Consumer Unit/Distribution Unit)
Power inverter and batteries

don't forget the heat recovery ventilation system.

as for "made mandatory", I'd say no - it's just far too inflexible. Adequate space for such facilities (where needed), yes that's probably reasonable, but a single dedicated space per dwelling feels rather inflexible. The best place for PV related gear might well be in the loft, heavy items like thermal stores in the basement, heat pump and batteries outside and the CU close to where the power has to come in (which often has to be close to the front of the property to meet supplier/DNO rules). On the other hand for blocks of flats, such items may well shared between many dwellings, so a plant room in each dwelling would be wasteful.

   - Andy.

Most of us don't live in a house that has all those places to put things.

Look at a modern terrace house.  Then ask yourself where the solar battery is going to go if it's not allowed in anything but a dedicated plant room or fire-resistant garage indoors, and can't be within 1 metre of a door or window outdoors.  Then you have the same problem as to where to put the ASHP, but that's also not allowed to be within 1 metre of the neighbours.

Most of us don't live in a house that has all those places to put things.

Look at a modern terrace house.  Then ask yourself where the solar battery is going to go if it's not allowed in anything but a dedicated plant room or fire-resistant garage indoors, and can't be within 1 metre of a door or window outdoors.  Then you have the same problem as to where to put the ASHP, but that's also not allowed to be within 1 metre of the neighbours.