I think that I've only taken my bike on the East Coast trains once, which was fine, although I was hurried up when disembarking at Berwick Upon Tweed so as not to delay the train; it isn't helpful when reserved seats are at the far end of the train to the bike storage...
I've had problems with Virgin Trains on the West Coast in the last year or two whereby I was nearly left on the train at Preston a couple of times, and Edinburgh once too, although at least that was the terminus. The only reason I was able to get my bike off at Preston on one occasion was due to someone else trying to get on with a bike. It took them a good five minutes to attract the attention of a guard despite being on the platform. Another time there were two other cyclists getting off at Preston who just carried their bikes through the passenger compartment against the flow of people getting on to the train; I had two panniers so didn't feel comfortable attempting that. I asked them to ask the guard on the platform to let me off once they had got off, although it took me hanging out of the passenger door and shouting down the platform in addition to them asking the guard to get any reaction. The one occasion at Edinburgh I had to wait until the driver was getting off the train to finally escape...
In all of those cases the 'train manager' knew that I was on the train since he had either let me on with my bike and even asked about my destination at the time, or I had shown my bicycle reservation ticket during the ticket check and/or asked about getting off with my bike at the relevant station. I think that part of the problem is that the train manager can swap over at Preston, but there is still a fundamental problem with communication since I believe that it is ultimately the responsiblity of the guard on the platform to let people off the train with bikes. I wrote to complain and received an apology and Network Rail vouchers, but I would much rather they just sorted out the issues...
Non-bicycle related, but I had a really bad experience with a Cross Country train at Leeds recently whereby I was waiting for a delayed train to Edinburgh, which arrived very busy to a very busy platform about half an hour late. I wandered down to my carriage and tried to get on, only to find a woman in a wheelchair trying to get off against the flow of people getting on... I got off the train again with a few other passengers to give her space to come through, only to hear the guard blowing the whistle for the train to go. Despite the fact that the 4-5 of us who had got off the train were shouting for the guard to come and help the woman in the wheelchair get off the train, to which the guard responded verbally but not with any actions, the next thing we knew was that he had blown his whistle again for final departure and the doors slid shut with the woman in the wheelchair still on the train and the 4-5 of us still on the platform, all completely amazed... We descended on the guard, who tried to claim that he thought we had been shouting to say that a woman with a wheelchair was coming along the platform wanting to get onto the train and that he couldn't delay the train for that, despite the fact that I would say that we were all very clearly shouting that she was trying to get off the train. Basically, he ended up saying to us in no uncertain terms that it was our fault that we had missed the train and that we shouldn't have tried to help the woman in the wheelchair, which is a pretty appalling message! I've written to complain to Cross Country, who have sort-of apologised at the same time as passing the buck to Network Rail, so I'll be very interested to see how they respond about the issue...
Any tips on "having to jam the doors of a carriage"? I did half-consider trying that with my foot during the Leeds incident, but didn't have the courage to try...