And for some reason I can’t seem to take the 747-400 off from Heathrow, even using the auto-pilot. I select the required altitude, and then put full throttle on once clearence is granted and the plane tries to take off but just stays sticking up in the air, but travels along the ground (if that makes any sense?)

Any help would be greatfully appreciated.

Are your Trim and Flaps set correctly?

You should be able to rotate the 744 EASILY from LHR.

B744 Manual HERE

3rd One Down, tells you all you need to know. 🙂