The closest match with the 1:25000 OS map symbols that I can see is #16 scree.
The circles are not shown on the 1:50000 map and there is no scree symbol for that map range either.
The circles are all the same size: perhaps there are just a few small distinct patches of scree.
I had a look through the symbols/legend for the ordnance survey maps here (PDF), and could find nothing that matches exactly the type of symbol you have shown.
The closest were boulders (under Heights and Other Natural Features), but these would be normally oval/irregular shapes rather than circles, and with a heavier weighting on the line. The other ...
Nothing appears there on the satellite view, although the tree cover could well be concealing whatever it is.
My best guess at the moment is that this is a fictitious entry that is added by cartographers to catch out copyright violators who blatantly rip off their work.
These fake entries also go by the names “Mountweazel”, “Trap Street”, and others ...