British Railways, Past and Present
Before and After the Beeching Axe: in 1963 the Beeching Report recommended the closure of a number of rail services in the UK. This page at Joyce’s World of Transport Eclectica has maps related to that report, showing the state of the British rail network both before and after the report, as well as maps from that report. (See also the links at the bottom of the page, whence I extracted the next two items.) Via Plep.
Richard Fairhurst is working on an historical atlas of British railways: at the moment, it’s a single-page, one-megabyte PDF file; the web version is offline for the time being.
Or, if you’d like maps of the present-day British rail network, National Rail has a page for you.