Elgin sold the Marbles to the British Museum round about the time of Waterloo (1815 - about fifteen years after they were brought to Britain). He received about half of what they had cost him; £35,000 or so as against about £70,000. With regard to the issue of his original intentions, I think it was only when he saw the kind of destruction that has been mentioned already, and indeed compared what was then present on the Acropolis with what had been there, and described by several visitors from England, only half a century before, that he entered into discussions with a view to buying those "pieces of sculpture which could be removed". Prior to that, he had had numerous plaster casts made under the direction of an Italian called Lusieri. These casts are still in the BM (or were until about twenty years ago; I'm not sure, now). Comparison of some of those that were made back in 1799/1800 with the originals left in place (i.e., on the Parthenon) show the remarkable deterioration of those originals; not just another two centuries' worth of wind and weather, but the effects of recent atmospheric pollution.   So, in effect, Elgin's "last poor plunder from a bleeding land" did preserve the marbles. If truly convincing copies can be made, and placed either on the remains of the temple, or perhaps even on a replica, that would satisfy visual requirements. Ah, but then there's the issue of value, isn't there?