1. When does this game come out in the UK? ;_; 2. What's the line clear delay/DAS etc. like on this game? Is it similar to Tetris Friends? 3. What controllers does this game support? 4. How's the online?
I can't really help you with the first two questions, but I can answer the second two. This game supports a bajillion controllers. Standard controls have you holding the Wii remote sideways. You can slap on the wheel if you want. The box has an image of the Wii wheel as a control option, but I don't really see the point. You can also use the balance board, nunchuk, or classic controller, and the online is compatible with Wii Speak.
The online modes are really limited. Just your basic Tetris battle. There aren't too many people playing online, but I didn't have that much trouble finding a game either. And the disc version is compatible with the WiiWare version, so if your friends downloaded that before hand, they can still play with you.
I don't think this has been dated for Europe yet, although I know there are people over there playing it, so they must have imported a copy.
The DAS and lineclear delay is faster than in Tetris Party, definitely faster than the default DAS on Tetrisfriends. See this post for more info: http://www.gamefaqs.com/boards/981421-tetris-party-deluxe/54995628
The back of the game case shows a nunchuk option, but it doesn't actually appear to do anything in the game.