Network Rail (interest declaration time, I work for them) has dozens of new and upgraded infrastructure projects ongoing all across the kingdom, of a variety of scales. Off the top of my head: Thameslink, Crossrail, Northern Hub, GNGE modernisation, planned electrification of the GWML & MML, rebuilding the Scottish Borders railway, Birmingham New Street rebuilding, Norton Bridge (WCML in Staffordshire) remodelling, and *cough* HS2 *cough*.
We who are in the railway industry are lucky that the overall picture is positive, with ever increasing passenger numbers and cross party political support.
As noted above, the railways of the late 1960s & through the 1970s followed the same depressing mantra that the UK was afflicted with in every aspect of public life - "managed decline".
There are some fantastic models of the BR Corporate Blue Era (have a look for the Bromley North layout by the way, before it is dismantled) but I find them gloomy, a reminder of a dark time, and it seems that a large number of others feel the same.
Still, it seems to get modelled more frequently than the more colourful post-privatisation / current railway scene.
Ben