Thanks very much. Yes, you're right, I may well be worrying unduly. As this will be first time taking the bike on a train though perhaps you understand my apprehension?
Of course it's not helped by the fact that I don't think I've bought a railway ticket for 30 years or more. I do very occasionally travel by train, but my wife handles the tickets. I might well bring her expertise to bear on this, though her knowledge of routes is all in the opposite direction, darn sarf to visit relatives.
Is "TP" TransPennine, aka Northern Rail?
My apprehension is why I'm considering "stretching" the three legs out with lots of room to manoeuvre if something is cancelled.
No Trans Pennine Express is NOT Northern Rail. Different company entirely.
At Preston station on the platforms used for the Glasgow and Edinburgh trains they have a live screen which says things like 'train has just left Wigan North Western' and 'train now waiting at something or other junction' and give the expected time of arrival and the general layout of the carriages.
As mentioned above, the platform staff will help you find the right place to wait for the bit of the train you need, just ask them.
I was on waiting just off that platform on Thursday, because it was more sheltered from the icy wind blowing on the little 'C' section of the half-platform my train would be coming in at, and I had half an hour to wait with my bike, and in that time two WCML trains came in and departed - one to Glasgow the other to Edinburgh. From what I could see, the platform staff were exemplary in directing people to the correct bits of platform for their ticket types.
I can give you full details about where to go with your bike when you get off at Preston from the Leeds train, for the Glasgow train. There's no need to hoik your bike up or down steps or stairs, it's all very civilised with lifts, ramps and underground tunnels.