Hi - I'm another Cammack originally from Boston, Lincolnshire, UK (first cousin of Canada-based Tim Hockey who has posted here before). I'm now living in London.
I once ran into a young female Cammack who was working as a barmaid in one of the London theatres (can't remember which one). I only knew because she had a name badge on! She said there were 2 Cammack clans in England - the Lincolnshire Cammacks and the Cammacks originating in Essex. I think she was also from Lincolnshire (Spilsby area, perhaps).
I also read in a Scottish book on the origin of names (in a bookshop) that Cammack means "great strider, or strong walker". Interesting that the only place I've found a name origin is in a Scottish book, which said the name was a Scottish name. It's also interesting that it's a great description of both me and my dad (Frank Cammack).
I'm 26 - and would be happy to get in touch with any Cammacks in London who are interested in making links to the Boston Cammacks.