I've come accross these bikes Electric bike

They look like
Battery 4Ah 36v (£195)
Motor in the front wheel (£235 including wheel)
Switch (50p)
charger (£70)

Prices are from the spares page on the website.

Now that sounds an easy ish project to put together (ignoring the fact I could never get my bike light project to work).

How much would it cost to build a 4Ah 36V battery and any suggestions as to where to get a wheel with a motor and freewheel built in? £500 seems a bit steep and they seem to be charging ~£1000 for all that built into a bike (cannondale capo £1650 with gubbins, £700 without)

Cheers for any suggestions/ wiring diagrams!

Martin