Im sure you have the answer flecc but how come a 250 watt bike with a throttle is apparently ok when it does not meet the either current UK law (200 watt) or EU law (no throttle) ?
It isn't, it's actually illegal and in theory it's use can be prosecuted and a conviction obtained. The only completely safe course is to follow the 1983 EAPC law, 200 watts with throttle or pedelec control. The next best option is the EU 250 watts with pedelec control only.
However, the law in this area is in a mess with various pieces of legislation in conflict and no e-bikes completely conforming to all requirements, so prosecution is generally avoided. It should all be cleared up in the near future with the revisions currently being worked on by the DfT.