So I looked this up last night for the UK as didn`t want to just be spouting crap - Will post the link below but the TLDR is that over a 250w motor and/or no assistance over 15.5 mph other wise its considered a motor bike and needs tax and insurance.
All the lads i know with regular ebikes have the de-restricted and bush closer to 30mph but that`s technically an illegal mod.
Got to love the nanny state. .
https://www.gov.uk/electric-bike-rules
All parks (the ones i've ridden anyway) do not allow twist a go on site - public parks may be different but I think not (its one google to many for me) as you do not ever see them on the trails.
Again dude, not hating. It`s a great machine, just with the way we look at them in the UK my mind goes straight to emotorbike
