That does put things in a slightly different perspective. But as has already been pointed out, the perimeter of this area will be within the flying range of a significant number of kept bees and the inference that this has a series of preserved colonies of a distinct type of bee seems to be of dubious foundation.
In the Ardnamurchan Peninsula in Scotland "The Apiarist" has said that because there are so few beekeepers in the area, bees are varroa-free. With sea on three sides and a wild and mountainous land barrier to the landward side., this is the sort of area where I would expect bees to have prospered whilst keeping under the radar. The area of Ardnamurchan is a more realistic 396km2. I have seen no claims that there are any numbers of "survivor" bees there, although admittedly, this is a much more hostile environment than cuddly Oxfordshire.