Several bike shops in our area are now hiring, selling and servicing e-bikes, but note that , just as with ‘normal’ bikes, specific brands will only be available at particular dealers. (for example my favourite high value brand ‘Cube’ is currently only available locally at J E James, although you can of course buy online from further afield, and if you want a particular model may have to do so, as e-bikes are made in relatively small batches, and dealers run out of specific models!
(Don’t forget to check for your Cycling UK/British Cycling 10% discount at Halfords)
https://www.ebikecapital.co.uk/ (Near Bolton – recommended by a Sheffielder)
Generally I would recommend that you really try to buy one from a localish dealer if you can, and/or one who is a BEBA (British Electric Bike Association) member. The ‘e’ part of e-bikes can be complex, and you benefit from close access to advice, follow up, warranty repairs and specialist service.
Otherwise you might be able to persuade a local dealer for a given e-system to undertake a warranty repair for you, but they will charge the associated labour costs, unlike the original selling dealer, but then that may be much cheaper than a round trip to the place you bought it….