I was lucky enough to go to a Q&A with the author at my local library last week. It was an interesting audience of interested readers, some folk who seemed to have wandered in by accident and a couple of hard-core Whovians since he'd written a couple of stories back in the late 80s. Interesting to hear him talk about his ideas and how the books had developed.
The covers of the books feature an interesting hand drawn map of London presented as a floating island surrounded by a water. and I managed to track down the website of the artist...Stephen Walter. There's something very fascinating about his maps of London and Liverpool and I can vouch for the accuracy of the London one at least as well as the comments that adorn the map ... you can't quite see my house but the comments sum up Sutton and Cheam pretty well!!
Have a look at the interactive maps here.....http://www.stephenwalter.co.uk/wp/maps/the-island-london-series/