A point to note is we're talking WW1's centennary so there will very likely be an upswing in interest for this stuff in the years ahead. Brace yourselves.
Some people think that after the centennary, WWI stuff will come down in price, I think these are the same people who said the same thing about US Civil War stuff in the early 60s. Prices never faltered, thye only went up, so I would agree with Laurie, if you see something that you want, and know it is real, and you have the bees and honey, then snap it up or you may never get another chance.
Gus