Although its all fine to look on the net, etc, I would suggest going to a proper shop, either independent, or a chain like Cotswolds or Go Outdoors, and actually trying some on. A Large is not always a large, the hood might drive you nuts, the pockets might be fiddly for you, etc. You shouldn't buy boots, shoes, beds, suits, packs, coats, suites or TV's without looking at them first - they have to fit and work for you (or your dad!).
As for materials, its up to the individual, but having had/have waxed cotton, LA Triplepoint, AQ2 (berghaus), Hyvent (TNF) and now 2 layer Goretex, the Goretex works best for me. You don't have to spend a fortune, but a good waterproof isn't ever a waste of money in the UK.