Next Generation Club World (as fitted to all 747 aircraft) does not require a special adapter of sorts. If you are using a UK plug you'll need either a European or US adapter.

I've used my laptop in NGCW recently, watching DVD's and processing photos and it charges up while in use absolutely fine. It charged from flat in about 2 hours, which is the same time as if I'd plugged it into a mains socket at home.

I can't comment on the WTP plugs, as I think that they do require a special adapter.