Rosie, that's a subject on its own, and it should be properly debated on this forum....
Buying on the net is tempting, but I believe, best avoided.
My personal view is the answer depends on how much you need the services of your local bike shop. For most people, e-bikes are just normal bikes with a motor and a battery added to. If they are used to look after their own push bikes, then buying on the internet makes total sense.