Mike
When the big storms occurred couple of decades ago I had a lot of trees blown down on the family farm. We milled it all and stored it. 10 years ago another farmer (Surrey by then) was clearing land and I bought 10 oak trees, 4 walnut, 2 (nearly dead) Elm and a few bits and bobs. I paid up to £350 per tree (really big mature trees) felled and trimmed for the good stuff. I had to hire a mobile sawmill to beam and plank, and we got a hell of lot of firewood as well. The green oak was all used to build a house and a barn. Most of the walnut is still in my storage barn. I hardly ever use walnut. The Elm was highly figured and got used for flooring (moves like crazy though). The rest was very mixed: maple, holly, chestnut. I gave most of that away or swapped for work. A local guy who does hedge laying converted quite a bit into charcoal.
It can be worth buying trees, but the storage / milling / transportation is an issue. Most of my oak is in Warwickshire. For stuff I am doing now, it actually makes more sense for me to sell the very seasoned wood, and import green oak from France. Price differential is 3:1. Transport and loading is a killer, and I don't have sawmill facilities handy here in Kent. I could use a portable set up, but the big issue for me is handling the big stuff. These days I only play about domestically anyway.
AJ