Lots of the rides I go on start and end in central London. I have been doing this on a Brompton for almost 10 years. There have only been a handful of occasions where I have had to take a car and I have either used the tube to get back home or simply cycled back - my preferred method.
I cannot think why anyone would want to drive into the the congestion charge zone for work, unless you have some sort of staff parking. You otherwise run the gauntlet of trying to find a parking space and even if you do, some will cost about £6 per half hour!
The powers that be are saying it's is your civic duty to avoid public transport but for many it really be there only way of getting in to work.
I imagine that many families will not want to use public transport for some time and the option to drive into London over the weekend to visit museums, art galleries, attend events, go to the theatre, see the sights, go shopping...will be halted somewhat as they won't want to pay the £15.
I don't think many of my fellow Brompton friends will care too much about all this and will just add the extra miles to and from the start/end location as part of the ride. I know I will!!