....The trainspotters at school (in London) used to talk about going to Crewe (apparently the Mecca for spotters).
I used to live in Chester and go through Crewe often on the train... banks of people with notebooks and cameras - quite impressive... 
I used to pass through Crewe a fair bit when I was at Uni if I was getting the train from Aberystwyth to Durham. Nearly every time I went through it was raining ...
When I was a kid, the real 'go to' places were Carlisle if you wanted a bit of electric action (plus it was a scenic trip from Newcastle with some guaranteed loco haulage, generally a Class 31) or Thornaby, so you could see all the Teeside steel traffic as well as the comings and goings in Thornaby sheds and Tees Yard (usually involved a trip from Bishop Auckland to Thornaby on a crappy old DMU, sometimes with a change at Darlington, sometimes not) - hell, we used to do overnighters at Carlisle when there was a lot of container traffic up to Scotland (generally double-headed Class 86s, sometimes a couple of 87s)
There are a couple of hotspots near where I live, too - having had a look round YouTube there's a surprising amount of footage shot from the car parking area behind my house, as well as at Colton Junction where the ECML and Leeds lines diverge - if the layby at Colton is full of neds, then there's a fair chance that something interesting is afoot.
Probably shouldn't say it, but one of the reasons I bought my current house is because it gives me a nice view of the ECML and I can just sit and watch the trains if I feel like it
