Its appearance readily distinguishes it from that real firearm (the Thompson). I can't fathom a situation where you'd actually be convicted under S36 for selling one, even if someone does go full Hudson with it.
This is in sharp contrast to S19 public possession, which I agree is a bigger, broader issue both for us and for wizards-and-hobbits types.
Having skirted round the edges of that community, there does seem to be a high quotient of people who are desperate to be
seen, but can't grasp how they're going to be
perceived.
They
will keep getting caught doing it...
https://www.bbc.co.uk/news/uk-england-essex-45994558
... resulting in some some knee jerk reactions from cons, gating the problem once it's already arrived at their door ...
https://www.nbcnews.com/news/world/fake-guns-are-confiscated-londons-mcm-comic-con-n451386
Hmm. "While Britain’s 2003 Anti-Social Behaviour Act means most replicas of guns must be concealed when in a public place"
I've seen this repeated a few times, but it says no such thing,
it only matters if you have it with you. Of course you should conceal any IF or RIF so that it's less likely to be an issue, but if you are caught, you're going to need a reasonable excuse.