Better off with an old Honda, something like a TRX300-350(Big Red) pick one up for about £1500 and still be worth that in a couple of years. Pretty much bullet proof.
4wd is a must unless you want to do 30mph over the wet bits
I have used quads a fair bit in Scotland, and some time ago decided to buy a good second hand one.
The first one I bought was a Kodiak auto. Lasted about 3 days and the gearbox siezed. Nice looking bike, but no thank you, got my money back.
I then investigated the whole Quad deal, and ended up buying the same machine that I had available on a lease I ran for nearly 10 years. For me nothing beats a Honda Quad. I bought mine about 3 years ago from Fieldens, second hand, re stoved frame, new tyres, complete overhaul, 3 months gurantee, ex RSPB bike, so it had been looked after.
Cant fault it, I have used it in Scotland and Dorset, and had two Red Stags on it, and three Sika (not all at the sametime I might add).
Honda are probably your best bet. Hope this helps.
A pal of mine has a selection of quads in various stages of life, he has a Yamaha, I think, 4 wheel drive one that I use when needed. The interesting thing is he has a couple of 2 wheel drive ones which he maintains are almost in the same league as the 4WD, the secret is in the tyres is his theory. I don't know enough about them to be able to give an opinion, but I am sure someone will know. I suppose it all depends on how extreme you intend to go with it, but unless you are planning on serious jungle bashing, it could be worth a thought. They do seem to be a whole lot cheaper, which is always good.
2wd drive Quads are a pain! They always let you down when you most need them. Thats usually when your making them work for a living. Either towing, pulling, or hauling. Like 308 I've fitted a winch to the front of mine, and use it.
2wd is fine if all you want to do is poottle about and save yourself some walking. If you want to use a quad for work get a 4wd one its the only way to go.