It is up to each guard whether they allow bikes on. Generally Central Trains (as was) services do allow bikes, although I sometimes wonder what the limit is. For instance on the very busy 1721 service from Nottingham - Lincoln I've seen 6 fixed frame bikes squeeze into a very limited space. I suspect if there was one more the guard might get fussy! Luckily the train is usually so packed that the guard can't get through to find the problem!
I've not had any problem, but then I can fold my bike and put it on a shelf!
The old Midland Mainline service - it will probably depend on the stock being used.
Certainly long distance trains usually sell tickets or give them (as on GNER now NXEC) just to make sure there is enough room.
Bob

Do not know if this is relevant as the Robin Hood line is run by east midlands trains but I understand there are one and the same. I regularly take my bike on the train I have never had problems with east midlands trains, there were a few occaisions under central trains when I could not get on the train and one memorable occaision at Hucknal when the conductor quoted the two cycle rule at me and refused to let me on. I did phone East Midlands/Midland Mainline prior to them taking over the franchise as I had heard that they charged three quid to carry a bike but they assured me the only restriction on them carrying bikes was the two cycle rule.

This is the response from the DOT to local MP John Heppell regarding this subject.

Thanks to Lex for taking this up with them.

cycles_on_trains.pdf

I have never have any problems, just turning up but then again I'm quite pushy.