I'll probably never use this service, but I'm sure I've seen people asking about where to leave their bags/etc if they can't drop them at their hotel early and don't want to drag them around...
I get emails from Heathrow airport which is where I originally saw the article about the Airportr delivery services.
Heathrow, Gatwick and London City take part.
Basically, they'll deliver your bags to your hotel/office/home address for you (maybe you are arriving early and can't drop your bags and don't want to lug them around or waste time getting to your hotel to leave them) or they will pick up your bags from your hotel (or office or home address) and take them to the airport where they will be waiting for you (maybe you have a late flight out but don't want to/can't leave your bags at the airport and don't want to backtrack to a luggage drop off at say, Victoria Stn or Waterloo to pick them up).
Price varies depending on which airport and where it is going in the city...here is the official website... http://portr.com/
Anyhoo, on second thought, this could be quite brilliant. There was actually a few times for me this would have come in handy - and compared to what we paid to leave bags at Victoria or Waterloo (7GPB a bag - sometimes with 4 bags because your little personal size counts as a separate bag!) and having to backtrack to pick them up and then go to the airport, it wouldn't have cost too much more!
I just thought people may find this info helpful!