Re: Careful there...
Über pay their drivers in London £5 per hour rather than the minimum wage of £7.20 (£7.50 from 1st April), they don't pay Employer NI (13.8% or £1 per hour) or VAT (20%). Driver expenses work out at about £2.40 per hour, Über charge around 30% commission, so about £10.50 per hour in total, and VAT on that should be about £1.75.
This is about £5.25 per hour they are avoiding by breaking tax and minimum wage laws, which is more than the margin they are currently making, and that is why they are so cheap.