Another suggestion for Kristin Bezio: sometimes, university libraries are willing to foot the bill for a faculty member or graduate student at that university to order a scanned reproduction of one or more documents, so long as you promise to deposit it in the library collection once you have finished using it. You might see whether there are small grants through your university or library to order a reproduction (which may well be less costly than a flight to London, depending on where you are located). –Jessica Wolfe