With regards to compatibility of Wii consoles throughout different regions, here is some information:
The UK Wii operates under a system known as PAL. The Wii console is region restricted, which means only PAL games would work on a UK Wii. Asian countries operate under NTSC, as do American countries. Because of this they would only play games from their particular region.
As for European countries, they all use PAL the same as UK, so because of this there is no issue in using a European Wii console to play UK games and the system should work fine. The only issue would be that you would require a travel adapter or a UK Wii power supply to power the unit correctly.
There is however an exception to the above, France operate under a system known as SECAM. Because of this we cannot guarantee that a French console would play PAL games.
As for warranty, we deal here with European warranty, so any console bought within Europe would have valid warranty with us here. An American console for example, would not.
If you require any other information, feel free to contact us.