Where are the cheapest places to pick these up online for UK. The wii versions seem loads cheaper but for what difference except the box? Or is the item more precise?

To my knowledge there is no difference except the Wii U branding.
I would pick up a normal wii remote plus.

All that seems to be different is the packaging.

I picked up some new Wiimotes in black, to match my Deluxe U console - other than having Plus built in (my original white Wiimotes didn't) they are nearly identical.

What they said. I would make sure to get Motion Plus for Wii U as some multiplayer games will require that. Also get some fashion colours. I have blue, black, red and gold motion plus remotes.