I think the chances of you being caught and taken to task over this are remote but, I will give you legal situation.
Unless you have consent to use the name, then you breach the intellectual property right of whoever owns the name. It is now owned by the National Railway Museum.
The most common litigation over things like this is with football clubs who are extremely protective of the name and image.
You can deal with this a couple of ways. You can simply go ahead and do what you propose to do and hope that nothing happens. Or, you could write to the National Railway Museum and ask the consent to do whatever it is that you’re going to do and perhaps tell them that you would make a small donation for the consent or from every item which has been sold. The problem with this latter course of action, although that is the most favoured, is that it does bring what you are doing to their attention and if they refuse, you are going to be on their radar although I imagine that they have other things to do than visit market stalls.
In essence, if you want to do this legitimately, you are going to need consent.
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