Mike I wouldn't get too carried away by out of town retail it is a very small component in the greater scheme of things albeit a very necessary one but my experience of London is that most people inside the existing zone would rarely engage in DIY or home deliver ikea type products themselves but would hire contractors.
Offices have had little effect as planning authorities have granted very small parking allocations for at least the past 20 years. I know of one 19 storey building with 4 spaces in total.
Retail High Street retail in W1/WC1/EC1/EC2 generally tends to fall into two main categories firstly volume retailers like Selfridges, John Lewis, Benneton etc who rely on massive footfall nost of which emerges from the underground and to a lessor extent buses and national rail. Secondly high end such as Bond Street and the smaller streets off Picadilly such as Saville Row, Jermyn St, Cork St etc most of this trade is to the locals who don't leave the area or to wealthy tourists who are staying at local hotels. I'd try to talk to the Dublin guys who own Thomas Pink for a fuller flavour if this is a serious thesis.
Industrial; there is a little industrial around Hammersmith but very little else; an interesting case study could be the DHL depot at Waterloo.
As it stands it appears to this observer that the charge has just become part of the furniture and that in the main City traffic is moving better than at any point in living memory. There are ways around commuting to work by car and by making it difficult you restrict all but the most senior employees