My father and I won a charity raffle trip in the BA 744 sim at Cranebank - it must have been about 15 years ago.
We had a two hour trip, and by the end of it I was poling it into Kai Tak with the training captain in the LHS prompting me and following me through on the throttles. I had about 140 hours SEP at the time. LHR was much easier, but I 'm sure I didn't do a solo/un-assisted landing.
Based on that experience I don't think it would be possible for a PPL to do it even with prompting from the ground.