Thanks for the offer Chris, I might take you up on it. But I've checked and the last trains turn out to be 11.33 and 12.03 from Liverpool Street, so it should be doable by tube.

Though, for Tottenham Hale, it turns out the last train is 10.53, and nothing more till 5.30 am. What a way to run a railway. How does it compare with the situation of people living 20 miles or so outside other capital cities, in towns with a railway link?