Just had a look at the site.
My thoughts? Cripes.
I doubt they are Greek btw, and would offer Cornish or Irish as a possibility. However, you can also get really well bred A.m.m. queens out of parts of France (there are some fine breeders of them there) direct by post for maybe one third of that rate, plentiful and early.
There are also a handful of breeders up in Scotland, one guy on the shores of the Firth of Clyde has A.m.m. with a fine reputation. At the price being asked they could be from any one of a number of smaller scale breeders then resold on.
They will in all likelihood be fine queens, but at that price are only viable as mother queens in a breeding programme.
If being sold on to smaller beekeepers as normal colony heading queens then I suspect there is a degree of taking advantage of the current revisionist fashion for having A.m.m. and claiming it as a virtue. As someone else pointed out, in a generation or two it will be subsumed into the pattern of local mongrels, although their owner may still make a claim about their specially sourced A.m.m. for years afterwards.
As mbc said, they are probably the product of a careful breeding effort somewhere, but unlikely to be West Sussex. The outfit in question, a fine company btw, is a trading concern that buy in and sell on, as well as being significant beekeepers in their own right.