There is no real height requirement other than it must provide enough head pressure to allow the top most parts of the system to fill with water, which would presumable be the upstairs rads not the cylinder coil.
The issue is more to do with the correct pipework design & installation, all intended to keep as much of the system under positive pressure when the pump is running at the same time ensuring that when it starts up water is not pushed out from the safety open vent pipe into the cistern. Lastly as much as possible of the extra water created when the system is heated remains in the within the cold feed as water moving up into the cistern when hot & then back into the circulating water when cold would introduce oxygen & promote corrosion.
F&E tank supposed to be at least a metre above the highest circuits in your heating system.
But extra long feed pipe is often better to ensure less air ingress into system.
But it depends on how it is all piped on your system.
You would be best to have your heating system sealed if it is gas or oil system.
There is very little cost to this normally.
The system will need to be sound though, - no slight weeps anywhere and radiator valves all with proper sealing glands, so no pressure loss
Look, what you should consider is how high you can locate your tank...not how low ..done the odd one over the years at min. spec height and they worked but the performance really was rubbish
in my opinion...or just rip it all out and go unvented