The only time I've driven into London (as in central London) in the last few years was to get to my old office to collect my stuff - on a Sunday. There wasn't much traffic, but parking was still a nightmare.
A car is often more convenient (say that 2am trip to Tesco to get something) but at other times, it's not really an option because of the inconvenience. And city centre to city centre by car is just asking for trouble.
As said above, there are many people totally unaffected by the recession and who are paid an hourly rate that doesn't permit them to waste time in a car doing nothing productive.
Likewise, there are many businesses which won't allow people to travel first class, so that's where you can perhaps offer an intermediate class, or make standard cheaper at off-peak times.
It might not always be possible, but when I'm invited into London for a meeting or interview, I often try and make sure it's after 11am so I can travel off-peak.