"don't expect to get off with four blokes in a Warrior"
Now there's something I had never thought of of doing!
But, to be serious, if a Warrior is within W&B limits, I do not see how you would have any problems in getting airboune off Denham's 779m of tarmac. Yes there are trees, but not very tall, & not very close to the runway. Also light twins regularly use that field. I have flown GA7s in/out of there.
By comparison, Elstree is only 656m. And Wycombe at 735m, is shorter than Denham.