We need us some more trees. *Eyes Mr. February.*
I'd also suggest putting some meat or tuna or something at the base of the tree. If there's claw holds for them and there's nothing physically wrong with them, it's pretty rare a cat will get stuck in a tree. It's more if there's a way for them to get into the walls that it becomes an issue. Having a hole put through your wall to rescue a cat is a bit of a problem, I imagine.
If that fails, I'd suggest the RSPCA. If nothing else, they can tell you who does animal rescue in your area and can come and get the kitty. Or just get a ladder and pop up yourself. Maybe put some oven mits on in case the cat freaks out a bit when you try and get her. Or even put a plank of wood against the tree so she can wander down.