Before I left, I put out an SOS for sources of haggis in London. It wasn't my particular desire, but that of my traveling companion. Well...come to find out, she didn't want haggis, so much as she wanted haggis in Scotland. We didn't go to Scotland.
I wasn't crestfallen, though I'd sure have tried it, but I wanted to thank everyone for their generous replies. I hope someone else will be helped by them.
Thanks to you all, again.