Thanks, Brian. I tried this link (or rather http://www.ordnancesurvey.co.uk/oswebsite/, to which it directed me) and it did indeed come up with a section of the 1:25000 OS map for the area, with contour lines. The trouble is, I found that on the scale available the contours were virtually impossible to trace in built-up areas, because they were obscured by the details of roads and buildings.

I've always wished there was a proper geographical atlas for (South) London, or our part thereof, which would show clearly (on separate maps, presumably) not just roads, but also railways, underground railways, political boundaries (including parliamentary constituencies and wards) contours, streams and rivers, sewers, water mains, geology, land use, flora and fauna, demographical data from the census (age, ethnic origin, income, ecomomic status etc). Anyone know of anything like this?