Sorry Chris - just gone back up through the thread and I had missed your original post - yes the 750W motor has to be treated as a electric vehicle so it has to be registered insured have a license plate and an m.o.t as it’s effectively an e-moped under uk legislation. It not illegal to have one but trying to use it uninsured etc is, just like it is for cars and other motor vehicles.
I still like this style but in the e-bike motor version of 250W which is ok under UK law and which seems to be quite an all around multi use sort of bike which takes a child’s seat or a load rack etc and suitable for the awful roads and paths around where I live.
Moxi