Wintertime: I finally got around to checking the cache today, and I was able to find it, but it took me nearly 15 minutes. The previous finder had put it back in exactly the right place, but the ivy has really grown up in that area.
I've decided that this cache has served its purpose and deserves a nice retirement. My thanks to everyone who looked for it. I hope those of you who found it enjoyed the Greenwich tchotchkes and other trade items. If you ever get to London, do take the boat down the Thames to the Royal Observatory and visit the Prime Meridian yourself.