You don't play games, you don't edit video's, in essence you have no need for anything more than a bog standard computer, what on earth are you considering paying £500 for????? My computer cost me just under £300 an plays battlefield 3 with settings set to high with a 1920x1200 resolution. The only way i could understand someone spending £500 to watch youtube video's would be if they are insecure enough to either need to look at it and think ooo, look at my pretty computer or are lame enough to think it'll impress other people, such as the majority of apple users. If you're going to buy one of these fancy all-in-one built into a screen jobs, then i honestly can't understand why you simply wouldn't buy a laptop. The only real reason to buy a PC over a laptop is either for intensive use such as games or editing or programming etc, or because you wish to have the ability to upgrade it. If i stopped gaming, i would sell my computers in a heartbeat for a nice laptop and a netbook, absolutely no point in them otherwise.
As said, why not just build your own. It's like a single digit jigsaw, hardly the most challenging thing in the word, especially when all the pieces have plainly obvious places to be put unlike with a conventional jigsaw. If you really want you can even buy a barebones system which means all you have to buy is a processor, ram, harddrive, and dvd drive, if you're not gaming then you don't even need to bother with anything more than the onboard graphics that comes with the motherboard.
