Always been a fan, I'm out of practice though!
Great TD! I'm out of practice though, only managed 10037 and died at level 39...
My Strat:
Place one cannon tower at the beginning so that it can attack both the entrance and the route below it, upgrade it once before level 1, then upgrade again before level 2. Let it for for 3 rounds, then make another cannon (and upgrade it) at the first U-turn. That will last you to level 7. Get the fire upgrade and sell your cannon towers, place that fire tower around the same spot that you had your cannon, but a litle to the right (make sure that you can still hit the entrance). Upgrade when needed, and only use your wood for interest at this point. Upgrade and add towers if needed, especially during the bosses, where i like to place a few in the middle as well.
Happy TDing!