2 things to say here:

I have just had this e-mail back from Frances Lynch; she is author of the CADW guidebook for the area, as well as an archaeologist.

I let the mail speak for itself:

"Names for sites are arbitrary in most instances and writers often choose
different versions,depending on which they think are the most notable nearby
features. The Druid's Circle is the only monument on Cefn Coch which has a traditional name. To identify the others people normally use the numbers in
the Royal commission on Anc. Mon Inventory for caernarfonshire East. This
is where Circle 278 comes from. I am not at home at present so cannot look
up the number of the Stones (2 rows and a cluster of jumbled stones) which I described in the Cadw Guide. As regards what they 'mean' I can't say more
than I did in the guide.
I read your discussion which seems to expect precision of location at a period before GPS. All the RCAM fieldwork was done in the1950s. Getting
up-tight about 8 and 10 figure grid references is pointless. Why not simply
go out and look at the sites. Prehistoric man is not going to have bothered
about the difference of a few metres on an arbitrary measuring system. If
there is any hope of understanding reasons for location, you have to visit
the site in person - and even then your chances of understanding motivation
are small.
Frances Lynch"

**************

Also, in keeping with my ID changes online, I'll soon be changing my TMA ID to Shropshire Traveller.

Cheers

Tim