Just something that struck me, say a company churning out repro signage with name/trademarks of a company that still exists, would they be flouting any copyright laws and would they (and/or those that openly sell it as a business) leave themselves open to legal action??

yes

I don't suppose there's any case of a trademark holder doing just that?

Or are they that bothered?

 Hi, I once bought a BP tin sign years ago that had been " worked on " to deceive ,

later on i noticed on the reverse in very small print "made by permission from BP".

so at leased some manufactures are honest but the dealers passing them off as geniune are not  .  Buyer Beware.

Regards.

Keith

Sorry my post was a bit vague, meant was there ever a case of a trademark holder going after a producer or seller of repros.

I do know there are companies that market 'vintage merchandise' like Guinness, that usually have something on the back saying that it's an officially licenced product.

I think the guy making the modern glass petrol globes got in trouble