I would suggest the £599 Oxygen CST HT kit, SWX02C rear wheel motor, 13AH battery and LCD.
http://www.oxydrive.co.uk/
Woosh only has MXUS XF07C rear wheel with cassette, Their kit with XF07C, 13AH HL battery and 18A HL1260 controller costs £500 but the SWX02C has much better torque than the...