I take it this is in the 'Cross Country Quick Mission'?
The easiest thing to do is to ignore the runway and allow the plane to turn to the right. There's a strong crosswind built into this mission (just watch the clouds moving) which makes it almost impossible to stay on the runway.
If you allow the plane to turn right, concentrate on avoiding the buildings, you should take off fine. Taking off into the wind is more important than following the runway on a grass airfield!
You do need full left trim and full left rudder in any case though, to counteract the torque of the engines. Reduce rudder as speed builds.
Good Luck!
