Well I've been taking my bike on trains for the best part of 20 years and I find it strange Northern should be coming in for so much criticism as in my experience they're the best TOC for bikes by far.
Recently I took the bike out to Garsdale from Leeds on a 158 + 153 working. To her great credit (and my amazement) the guard somehow managed to cram no less than 9 bikes on the train, at each stop coming out onto the platform to advise the boarding cyclist the best place to put their bike. She could quite easily have done the jobsworth "2 bikes only" attitude but no, thanks to her, 9 cyclists enjoyed a fine day out.
Personally I find TOCs who insist on compulsory reservations the worst, in particular EMT. I would much rather take my chance on the cycle spaces being unoccupied rather than face some stroppy guard refusing to let me on even when the space is vacant just because I haven't prebooked. The other issue with prebooking of course is that on a day's cycling it's very difficult to estimate how long your ride will take and whether anything unexpected such as bad weather or a puncture will mean you need to get a different train back.
So no, I'm happy with Northern's turn-up-and-go policy and, so long as it's not the last train of the day, will respect the guard's wishes if he feels the train is too crowded for my bike. It's a pity the OP didn't do the same.