Sets are really fun to make if you were talking to me. Go to a local DIY shop with lots of wood and ask them to cut out the sizes of wood you want. I did that and went back 10 mins later and it was done. I also made mine so it could be portable with these joints. All you have to do is attach one or 2 to the wood and then the other half to the other peice of wood and then screw them together and its all in 1 peice, then screw them out and its back portable. That may sound weird!
I think a really good place to go to is a Model Train Shop and im lucky because I have one down my street. From there you can buy Grass, Fake Snow, Sometimes Hedges, Road, Path, Allsorts. You can even buy Wallace and Gromit Airfix!
Ohh and also I got from the Model Train Shop some brick paper for houses, I think my set will be finished in quite a while but I will take my time! 
Harry.