U.S. receiver or one bought in London for use in London? Differences?

Unless you can find one that has a 120/240V switchable power supply best bet is to get one when he gets there. Also, the different TV-signal standards over there may not work with a US model.

At least in Sweden (I presume it the same in UK) one can buy power converters that transform to 120v (with optional W power, ranging 200, 300 and 800w), price in Sweden is from 28£ (200w) to 64£ (800w), the 800w unit weight 9 kg (18 lb's), price is probably a lot less in the UK.

The power converters looks like a black box with a domestic power cord to the wall socket and then one or two US outputs on the converter. This will guarantee that your receiver run on the correct electrical specifications, if one is cheap just get a wall plugged transformer but then your receiver will probably not last long since the wall plugs don't transform the voltage just the socket.

Some receivers have build in switch for switching from 120v to 220-230v, this can be done by one self, but I recommend a certified electrician to because sometime welding is involved, but take notice all receivers doesn't have this switch. You need to take of the receivers chassis to perform this task.

Most European TV's are able to play NTSC, but only in video mode = HDMI in, component in etc, so that should be no problem, just read you TV's manual to be sure. On some Euro versions of receivers one can switch from PAL to NTSC so I guess that should be the other way around if one buys a receivers in USA as well.

Picture:
http://www.kjell.com/content/media/i...tems/44099.jpg

IIRC a ~1kW (!!!) power transformer is something like $60-80 on eBay and it's the only thing you need to buy to use your lot cheaper US unit in London.