Excess Baggage
Offers baggage storage facilities at London's major airports and train stations.
http://www.excess-baggage.com/

London City Airport
The contact details of the left luggage office at the airport.
http://www.londoncityairport.com/pda/lostpropertyandleftluggage/index.asp

Luggage Minder.com
A luggage storage and laundry service that will collect from and deliver to any central London address.
http://www.luggageminder.com/

Talking Cities
A short note on left luggage facilities at London's main airports.
http://www.talkingcities.co.uk/london_pages/essentials_jl.htm

Transport for London
Contains information about the left luggage facilities at Victoria coach station.
http://www.transportforlondon.gov.uk/vcs/facilities_luggage.shtml