Originally Posted by
Gameguy
It's basically already been said but there's a few ways to look at it. If you're just wanting to use the N64 then a North American power supply would be the best thing to do, it would use less electricity too as these step converters use more power when converting the voltage. If you're wanting to use other devices like that Xbox you mentioned then a step converter would probably be more suitable, or use a North American N64 adapter and still get the step converter anyway for everything else.
As for the other adapter you posted, this would go with my previous statement of "cheap adapters" and aren't worth bothering with. I'm going to assume the adapter you've already been using with this UK N64 isn't even that good and just adapts the shape of the plug as I originally thought. If you're patient you can find proper step converters for better pricing, I found one at a thrift store that works pretty well and was under $10 with tax included. You have to be lucky though. Just another option if you're not in a rush.
To anyone else asking about the TV, he said that he's using a TV that previously worked fine with it. I'm going to assume that it's a PAL compatible TV and would continue to work just fine with these UK systems.