Bikes on trains in the UK

Sorry to revive an old thread! But i'm possibly coming down to London next week to buy and collect a bike, bringing it back on the train. I know i've to read the individual train companies policy and i have done, it will either be East Coast or Grand Central trains, however i was wondering if anyone has ever been turned away from a train even with their advanced booking because they have a bike? It's something i'm quite worried about happening haha, wouldn't really enjoy having to pay out for another train with no guarantee i can get on it.

I would be going from Wakefield - London Kings Cross, if anyone could shed some light on if they've been turned away or anything about kings cross regarding bikes!

Make a reservation, it is free. Job done.

The problem without a reservation is the bike storage is not necessarily where the guard is. If the reservation is made, he will be in the correct position waiting.