Smallpilot from an ATC point of view, if an A/c requires to hold off to burn fuel (or other reasons - checklists etc), the best place for it would be in a position where it won't get in the way of other arrivals/departures (Unfortunately, the LAM hold at LHR wouldn't be the most ideal place). Other considerations would be given the navigational equipment of the aircraft and surrounding nav-aids if they were required. And depending on the problem, I wouldn't want it too far from the field should the problem deteriorate into a situation where a quick return could be necessary.