These bikes have a rear number plate bracket already in place and have the EU's EN15194 certification. The certificate copy is available to buyers and armed with that there is no reason why the Vehicle Inspectorate could not approve use as a moped, subject to compliance with moped regulations as David has said.If you passed your test before February 2001 you would not need a CBT.
https://www.gov.uk/cbt-compulsory-basic-training/overview
Also worth pointing out that some companies are already selling s pedelecs in the UK. Often with no mention of the legal side, unlike 250 watt motors there is no grey area.
Example:
Kalkhoff Endeavour BS10 XT 50cm
Wisper - David, just wondered what would happen if someone tried to register this bike and adhered to the laws currently set out for mopeds? (i.e. registered, registration plates, insurance, pre 2001 licence or CBT etc).
After all, the petrol powered bike-motor kits and bicycles like the VeloSolex of the 1940s to the 1980s were all registered, plated and licenced for road use as light motor cycles, as were their predecessors from the 1930s on, the pedal equipped autocycles, so precedents exist.