Yes, yes it will. Hardware is hardware, it all conforms to the same standards, regardless where in the world you buy it. The only component you mighthave slight problems with is a PSU, unless it either switchable, or auto-sensing, like most of them nowadays. Other than that, you're fine.
But I would have to say, just because the hardware is British, DOES mean its better ;O)
The most annoying thing with international hardware is getting driver updates for your stuff, but with a video card you should be fine. I just remember having to jump through hoops to update the drivers on my Soundblaster Audigy because I bought it in England and the site was crap back then (2001-ish).
Here are some possible problems:
1. As mentioned, video functions may be PAL or even the other NTSC.
2. DVD drive, or DVD software may have problems with the Region Code.
3. Power supply (and cord) may require adapter and/or switching for voltage.
4. Some hardware, including video cards, are coded for their target locales, and installation software may install a different language.
I had a canadian card destined for the UK, and it did all kinds of wierd stuff on installation. (But it worked fine once I configured it for NTSC and pulled all the PAL code oot).
Again, just to re-iterate, voltages and other intnternal specs will NOT be any different. The hardware in PC's is pretty much universal no matter where you buy it, the only difference is the language the drivers are in.
If you buy a machine in the UK, then upgrade with parts from France, Germany and the US, it'll all work together.
As for the TV output, yes, you can normally select either PAL/NTSC. Some even auto-detect. So, no need to worry, just buy the damn parts already