My name is John, I live in the UK, I am very interested in building my own electric bike, it would save me £100's of pounds in petrol a year on just short trips to the shops and they look like a lot of fun.
Hi John! Have you considered a gas engine motorized bike kit instead? I only mention it because of the KPG and the carb systems are greatly improved from their ancestors, and charge time isn't an issue.
Hi John. Why not buy a complete bike? ebikes in the UK are still fairly new / specialist, and you will find it much more cost effective to buy a complete bike rather than attempt to make it yourself.
Also if you buy complete it will mean it complies with he law on what is an ebike and what is not, for basics, see here http://www.kinetics.org.uk/html/uk_law.shtml if you build yourself, you will be looking at (possibly), MOT's and insurance which will destroy any cost saving you are making by not driving