This is actually quite an interesting question which is difficult to answer fully. But in response to most of the other replies, it is quite correct that the force of any Law is absolute, and is quite independent of a person's access to the law as written. The European Convention on Human Rights (ECHR) requires persons to have access to Justice, requires Decisions in Justice to be available in writing, but it doesn't, in itself, require Law (in all its manifestations) to be published.
I've dug out my dusty copy of Barnett's 'Constitutional and Administrative Law' to help me.
The "Statutory Instruments Act" 1946 makes clear the process by which Laws (not Bylaws, but please bear with me) are created, developed and enacted. They will be available (in England) in The Stationary Office and the House of Commons Library - an excellent resource in my opinion, and one which is often overlooked.
Others have raised doubts about the written record in the past, but there is no escape: "No one may question the validity of an Act of Parliament". Classic authorities are 'The Princes Case' 1606 and often cited more recently, 'Pickin vs British Railways Board' (1974) which affirmed that "the supremacy of Parliament" was effectively demonstrated by the revolution of 1688 [Lord Reid].
As for Bylaws, these are most recently endowed with the force of Law through the 1972 Joint Committee on Delegated Responsibility; this defined many ways in which Law may be made other than through Acts of Parliament. Some notable inclusions are the Decisions of Judges, Resolutions of the House of Commons, Local Authorities by way of Bylaws and public Bodies by way of Bylaws - that will include the Railway Bylaws. These are not required (to my knowledge) to record their actions in the HoC Library nor in the Stationary Office, but to maintain their own records of their own decisions. There are several model conditions attached to the Delegated Authority such as requiring the House of Commons to Approve them or giving the House of Commons 40 days to reject them; clearly these would require the Bylaw to be placed in the HoC Library.
Crucually, bodies who are empowered make law by virtue of the Statutory Instruments Act (Bylaws) ARE required to publish those Laws. The authority is R vs Sheer Metalcraft (1954):-
Where the offence in question consists of a contravention of a Statutory Instrument it will be a defence for the accused to prove that the Instrument had not been published (at the date of the alleged contravention), "It is then upon the Crown to prove that, . . . . , reasonable steps have been taken for the purpose of bringing the instrument to the notice of the public or persons likely to be affected by it".
There is an earlier Judgement which refers to Orders which had not been published at the time of the alledged offence in Johnson vs Sargant "I am unable to hold that this Order came into operation before it was known." But this won't help us with Railway Byelaws which may be known but just not accessible by someone.
Parliament is not required to scrutinise delegated legislation and due to the sheer volume (about 3000 items per year) would be unable to. However, delegated legislation (incl Railway Bylaws) CAN be scrutinised in the Courts; this may be in the course of a Claim, a Civil or Criminal action, by a Judicial Review, or in the course of an Appeal.
These delegated law-making powers cannot then be delegated to another. (eg to a TOC).
In the case of the British Railways Board, then it is (was) for the BRB to make available its Bylaws. That requirement would (I assume, for I have not checked) have passed to a successor - I don't believe it was the SRA later ORR so presumably passed to ATOC, and I expect the prohibition on delegating powers also would have passed to ATOC (preventing delegation to a TOC). This is hopefully defined somewhere in the privitisation documents (but which I do not have).
The short answer, then, is I would ask to see a copy of the Railway Byelaws from ATOC and not necessarily at a station. I would not expect any Court would be able to consider a Defendant's difficulty in obtaining a copy. Indeed there is no requirement for a citizen to be able to read at all (never mind access to a computer); but we are all subject to the Law.