Users of Rick's Easy Access Europe book on mobility issues

I'm taking my son, who uses a mobility scooter because of musular dystrophy, to England and Paris this June-July. Has anyone found significant information from Rick's book (2004) to be outdated? I hope we're setting on housing. I'm more interested in transportation and sites of interest.1) getting from Gatwick to the Tower of London area. We're renting a car to travel throughout the Cotswolds and will need to return the car somewhere and then take the Chunnel to Paris. 2)What's the best way to do that? 3) Any differences in the sites of interest in London in terms of mobility? Is the London Eye accessible? Thanks so much