The larger model (A4000) says 16amp 3200w, so this sounds like too much
for standard UK wiring.

It will need to be fitted to a dedicated 16A circuit from the consumer unit.
It could either be hard wired, with the plug cut off, or you could fit a 16A
Schuko outlet.

You probably shouldn't wire it up to a ring circuit. This is because (a) it
would not be protected at 16A like it expects and (b) it could easily
unbalance the ring circuit.

Christian.