Supposedly it was a three film deal, which ends with Quantum of Solace. But Ford Let them use Aston Martin for Quantum of Solace.
That aside, the only likely replacement is Lamborghini. But they aren't British, so there we go.
Jaguar are too cheap, really, and Bentley too soft. Rolls-royces are for Goldfinger, and Lotus aren't glamorous enough.
Morgan?
EDIT: Associated with ford? Roush? Saleen?