Unfortunetly, there aren't many other options at Heathrow. Occasionally the Royal Suite stands may be used if its a short visit & they're not needed for other traffic. Likewise, some of the T4 stands are occasionally used depending on parking.
I don't think BAA are too interested with GA at Heathrow, especially since Metro's hangars were torn down.
Depending on the customers requirements (& aircraft size), there are plenty of other options around London; Farnborough, Fairoaks, Blackbushe, Biggin Hill & Luton with all the above a short helicopter ride to Battersea (or a slightly longer drive to Central London)
Fried Chicken