Has anyone purchased rail tickets (individual tickets, not rail passes) from the US before heading over to the UK? I'm wondering if there was any trouble making the purchase and getting/using the tickets (I ask because doing so through the Italian rail system was a nightmare, but through France's TGV was smooth as silk).
Also, is it worth purchasing in advance - by that I mean, is there a significant discount compared to purchasing tickets when I get there? The national rail website makes it seem so, but I was wondering if anyone knew from practical experience.
FYI - We'll probably only be making a few train trips - London to York, York to Edinburgh, Edinburgh to London. That's the plan so far anyway.