Thanks for all your advice. I had heard that it was a good idea to put cat6 in alright. They say it's more reliable than wireless at present, especially for copying large amounts of data. I'll say it to Dad, though he won't have a clue what I'm on about!
In what cases would 'chasing' be involved? I am guessing that it means that if wires aren't where they should be then the electrician will have to drill in to the walls?
Also, would there be any advantage to me picking up fittings? I saw there on bargain alerts that fittings are currently going cheap in B&Q.