For those that haven't spotted it, realtimetrains.co.uk has had a bit of a makeover last month and had its functionality increased.
There's a whole host of improvements, you can now see freight movements which will be a priceless addition to enthusiasts (not sure whether that was available before, but I don't remember seeing it?). It also now looks good on mobile devices and when you select the 'more detail' tab when looking at a train you get location reports down to the nearest 15 seconds in locations with modern signalling - the absolute accuracy of which might not be perfect, but that's more accurate than any system I've seen including internal railway systems - even the Working TimeTable only goes down to 30 second intervals!
There are also stock movements listed for some services (formed off and forming at terminating locations), and the sheer number of reporting locations in some areas (for example 30 between London and Reading!) allows you to keep an eye on where your train is in a detail not seen before.
Full details of the update here:
http://blog.realtimetrains.co.uk/Recommended.