I've never seen a guard refuse a cyclist - the only times I've seen cyclists fail to board a train is when there is no sufficient space anywhere on board.
156s are good - they actually have a space designed for 4 bikes.
It's pot luck with 150s - in my experience /1s are better than /2s, and the ex-London Midland units are the worst. I don't think most adult size bikes actually fit in the bike area properly on them...
Pacers are so-so. You'd just have 3 bikes stacked against each other against the wall under the luggage rack at one end.
I don't know about 158s but I can't imagine it being fun.
Never been on 153/155.
And if it was TPE (ugh, hate their approach to cycle storage), there'd be space for 2 at best in the designated area - any more and you start to block the aisle.
But, usually either there would already be several bikes on the train, or someone sitting on the folding seat that probably won't move despite the sign on the wall telling them they have to. Personally, on 185s, if it's quiet I just go to the end of the train between First Class and the disabled toilet. That area is much better suited than the actual bike storage area, and I've only been asked to move to the actual storage area once, when a man in a wheelchair got on.