It's all very well saying trains should be bigger and have more seats and more cycle space and more luggage space, but we don't have that and no-one will be willing to pay for it anyway.
It isn't a question of "all very well" - it is the fundamental cause of the problem (which itself is only a minor aspect of the problem of overcrowding in general). Refusing to engage with it on the grounds that it's too hard simply means that the problem will continue to exist but a lot of effort will be wasted on "solutions" which don't actually solve anything.
This thread is a fine demonstration of that futility. We have people proposing draconian measures such as banning bikes altogether, people picking nits over whether one variety of bike is better than another, people arguing over whether one particular individual should or should not take his bike on particular routes at particular times, people who do not themselves take their bike on trains refusing to acknowledge the value of being able to do it, and nothing remotely constructive emerging from the mess.
Buried in the sea of words are comments from three or four people pointing out that the problem used not to exist at all, because 1950s DMUs had a proper brake-van area with plenty of space for bikes. The rot set in with the introduction of the 1980s DMUs which, as well as having less passenger space overall than the trains they replaced, had no brake-van area and whose token gesture at providing accommodation for bicycles (or indeed any other large and inconvenient items that people might find it necessary to bring with them) consisted at best of a seating area where you were expected to argue with the people sitting in the seats in the hope that they would move so you could put your bike there instead, all the way down to a tiny cubby hole that could take one bike and then only if it didn't have handlebars, or even nothing at all.
This style of design, despite being patently rubbish, then somehow became a "standard", and the same errors were perpetuated in all subsequent new stock.
If the problem of bikes on trains - and the greater problem of overcrowding of which it is a minor aspect - is to be solved, and not just niggled over, then it
has to be a long-term effort, and dismissing such solutions out of hand without even discussing them is not a sensible approach.
What needs to be done to make progress possible is to first eliminate the idea that inadequate 1980s-type interior designs are an acceptable way of doing things. They aren't. They weren't at the time - see the post about the first day of 150 operation on a branch used to 1950s DMUs - and they are even less so now with ever more people travelling by train. (Perhaps a good first step would be to compel those responsible for designing passenger accommodation to suffer at the deficiencies of their own creations.) A standard of passenger and luggage space of "at least as good as a 1950s DMU" needs to be set, and followed, and the current standard of "if it's like a Splinter it's OK" weeded out root and branch.
1980s DMUs are now as old as 1950s DMUs were when the 1980s ones started to replace them. It would therefore appear that they themselves will be considered due for replacement before too long. We need to make sure that before this happens, it is firmly established that new trains should be provided with as much interior space and as many vehicles as possible, and equally firmly established that the current idea of providing as little/few as possible is not remotely acceptable.