I feel really cheap promoting this sort of stuff but try anycabs.co.uk - it's a bidding system and so prices are consistently quite low. Also, I've also gotten

I feel really cheap promoting this sort of stuff but try anycabs.co.uk - it's a bidding system and so prices are consistently quite low. Also, I've also gotten decent cars, never had any trouble with people not showing up (even when I've gone for the cheapest bid, expecting crap cars). I've been in brand new Priuses, new BMWs and decent cars altogether (different companies and YMMV obviously but it's cheap). I've also had drivers really impress me by not letting a fully closed-down M25 slow down my transfer to the airport. As a price point, I've always managed to go Docklands to Luton for under £50.