How UK e-bike law shapes what you are buying
In the UK, a legal electric bike is an EAPC, which stands for Electrically Assisted Pedal Cycle. It must have a maximum power output of 250 watts, assistance must cut off at 15.5 miles per hour, and the motor must only help when you are pedalling. Any bike that breaks those rules is classed as a motor vehicle and needs insurance, registration and a licence.
Some bikes sold online, particularly on auction sites and imported from outside the UK, have motors that exceed 250 watts or a throttle that works without pedalling. These are not legal to ride on public roads in the UK, and you will find them on every marketplace, including this one. Cyclesite does not vet motor power, and a listing being live here is not a statement that the bike is road legal. Sellers tell us whether their bike is a compliant EAPC and we show that answer on the listing, but it is the seller's word, not a check we have carried out.
So read the listing before you buy. If the title or description quotes a motor above 250 watts, offers a throttle that drives the bike without pedalling, or mentions derestricting or unlocking the speed limit, treat it as a motor vehicle: on a public road it needs registration, insurance and a licence, and riding it without them is an offence. If the seller cannot tell you the rated output, ask for a photo of the motor label before you hand over any money.
Twist-and-go throttles are allowed only in a narrow set of circumstances. If the bike was first sold before January 2016, it is permitted. Newer bikes may only have a walk-assist mode that works up to about four miles per hour. If you see a newer listing claiming a hand throttle works at full power, the bike is likely non-compliant.