A very interesting and very emotive topic, for all who concerned, the UK uniform act is a slightly woolly piece of legislation, but the intent and spirit of it is designed to criminalise those who would seek to gain from the impersonation of someone entitled to wear a uniform.
In the US, they have the "Stolen Valor" (American spelling, sorry!) Act which is specifically aimed at "Walts" passing themselves off as something they're not.
Ours is a game/hobby/sport and is participated in by all of us for many different reasons but the aim of it all is fun. Simple.
If you want to wear something because you have a link, either personally, or via a relative or organisation, fine. If you want to wear it because it looks cool, fine.
If you try to pass yourself off as a steely eyed ninja SF super warrior and underwater knife fighting instructor from the 314th Mobile Mess tin repair unit (bath and laundry division) then don't be surprised if some people (ok, yes Me!!) fall about laughing!
No one has ever accused me of trying to be a rock star or being Billy Joe Armstrong because I wear a green day t shirt! (and if you heard me sing, you'd know why!!).