Thing is, the Falklands mod make ships in sections usually, like their Hermes Light Carrier. You get the bow, stern and middle sections, and place them down as empty objects in the editor. Obviously, that means they can't move, but since most fighting involving the Royal Navy was done at anchor, it's no big deal. I actually think it's a better idea than making a huge battleship that can move, since they're really slow, and are basically eye-candy.
On the subject of the British using destroyers over battleships, it's partly because they're cheaper, need less crew, are faster, more manueverable and don't need to be moored offshore or in a huge, specially-built dock. Besides, the Royal Navy's one of the best navies in the world, and has a tradition of going up against crazy odds and coming out of it pretty much alright. The advent of the aircraft carrier pretty much sealed the fate of the battleship and battlecruiser, since one plane with torpedoes (or anti-ship missiles nowadays) could sink a massive ship if it got lucky. Also, planes can deliver ordnance much further inland than a gun can, and with greater accuracy, and if a plane can't get in, a cruise missile could do the job just as well.