I have broadband at home and run it through a modem router to 2 PCs. One is upstairs and I have CAT 5 cable running through the loft, out of the bedroom wall into the PC which is fine. Now I want to install a network wall socket, fixing that cable into it making it an active network socket, and then plug some cable into it from any PC to make it work. So this is possible yes? If I buy a wall outlet, is it easy enough to connect the cabel to it? I've done a phone socket which is pretty easy, is it the same kind of thing? Cheers.

It's very possible...and not very hard to do. A network walljack is similar to a phone wall jack. One is RJ-45 (network), the other RJ-11 (phone). The style of walljacks we use at work differ only in color (and of course the size/type of plug that can be plugged into them). We use blue for network, white for phone. You will need a punchdown tool unless you purchase the type of jacks that do the punchdown themselves (I don't like that type as much). So take a look at what's available and go with what will work best for you. I'd use the type that punchdown myself but then, I do network support for a living and cabling is one aspect of my job so I already own a punchdown tool. Decide which standard you're going to use in advance (either A or B) and ensure both ends of the cable are wired to the same standard. The walljack(s) you purchase should have the color codes marked on them to make this easier.