Check out Hillside Road, Ewell in google maps.
and check out the links below to a film written by Michael Frayn in 1978/9.
It makes a really good companion piece to Metroland - the film I recommended to you by John Betjeman.
So take a break from your revision for an hour and enjoy the film. It's absolutely fascinating. If you like this sort of stuff.
About 4 minutes and 20 seconds into Part 4 of the film you'll find the tunnel he writes about in the novel.
Three Streets in the Country by Michael Frayn
Part 1
Part 2
Part 3
Part 4