I should probably be more incensed that my council has written to tell me that basically there will be no refuse collection service from here to eternity and I need to be turning the garden into a landfill site. But I can't help but wince at "Trade Unions have announced ..."
Now, I was taught it was Trades Union like Directors General and Courts Martial but instinctively it doesn't feel the same. General and Martial are adjective, Union isn't? Wiki reckons the proper plural is Trade Unions particularly as most represent a single trade rather than a group of trades?
I thought it would depend if there was more than one union involved as there can be more than one trade within a union. The one I'm in has a load of different trades in it. It may involve Unison and possibly Unite - so two unions.
Or my lack of grammatical ability may now be glaringly obvious.
Fowler's Modern English Usage: 'trade union (not trades union). Pl, trade unions. But Trades Union Congress, abbrev. TUC.'
Trades union doesn't make sense as a plural for several unions, as trade is an adjective here, so it isn't analogous to courts martial. There's something historical going on here though, because you're right, trades union used to be common. Possibly the TUC is a union congress for different trades, and trades union became current because of that? Waffle, ramble.