Battery Vehicle Society

These are awesome trikes but come in at about the price of a car! esp if you go for the more powerfull motor option (which will get you and half a ton up any of the hills around here).anyway look and decide for yourself they are based in bath and ship around the world..
http://www.cyclesmaximus.com/

Badger

Very heavy though, if you breakdown and need to push and pedal !!

I like the photo about halfway down this page: http://www.cyclesmaximus.com/electricassist.htm#lynch

I can just see it: "Oh yes officer, it's a 200 Watt system"

One idea I thought would be fun would be take one of those little trailers you can get for hauling kids around and install a motor and batteries underneath the floor where no one can see them. All you have on your bike is a throttle control, which you connect up at the same time you hitch the trailer to your bike. Would be fun for shopping at Asda.

You can buy electric assist trailers in America and I know a couple of people who have built their own here in the UK.

The benefit is that you have a normal bike when you want a normal bike - without all the extra weight and hassle of an electrical assist system - and an electric bike when you need the extra oomph.

Mind you, the ex-CTO of Tesla went one better - he had an electric Porsche 944 that he built himself with a petrol engined push-along trailer as a range extender