"Never flown heavy jets so this may be a stupid question, but would the flight crew in this case have deliberately pumped fuel to the left wing tanks in order to shift the centre of gravity and reduce the chances of a strike on a right engine during landing?"
Not a stupid question "DNS" but there are other "problems" with reducing fuel in one wing by selective dumping/engine feeding/crossfeeding using the overhead fuel panel.
I am sure the 747 fuel system is basically the same as the 777 that I flew, that is the first fuel tank(s) to be used are those in the centre/body part of the aircraft. To take it out of the wings would increase the "bending moment" at the wing root with all that weight inboard rather than outboard in the wing tanks.
So if we look at the Virgin flight the loss of No.4 hyd system would have required, once a return became the "plan", to dump fuel down to reduce the a/c weight down to below the max landing weight. It was not until (earlier than normal during the approach I would suggest) the alternate gear selection was made. Up to this point the loss of No. 4 hyd system was no real problem. I presume what followed was a discontinued approach and then the excursion to the south coast for further reduction of the landing weight by dumping or (with all that extra drag of most of the gear down) simply flying a few racetracks while coming up with a revised plan.
Personally, having dropped the gear on the first approach (on the alternate system) I would have been very reluctant to select it up on the main system without discussion with "those who understand the implications" more than myself.
At this point, to answer your question, "DNS", as long as there were no problems with leaving too much fuel inboard (the bending moments problem) it would have been very simple to have, by pump/crossfeed selections, to have fed all four engines from the starboard wing tank, reverting to "normal" feeds for the approach.
Basing this on the 777 fuel system I wait to be shot down by those 747-400 drivers out there..