You go out in your car, drink, ScooterMan [requires Flash] arrives on a moped, and drives you home in your car, with the moped in the boot. London, within M25 only.
Apparently (Claire here at work tells me) there's a company One for the road who do the same thing. She says the scooter's tiny and looks pretty stupid but the bloke on it was nice enough. And it costs more than a one way cab, but it's cheaper than that and also getting a cab back the next day to pick your car up. I'm told it's worth it just to see the scooter.