Cerrig Meibion Arthur 1
Image by postman

Try service stations along the way. Usually they carry local stock of OS maps, so you'll have to try looking between St Claire's and the Preselis.

Alternatively, Carmarthen is a good place to stop for WHSmith, Woolworths etc. It's on route from Glastonbury.

Kammer x

If you stop in Carmarthen to try and find a map in town, your best bet is to park at Tescos. It's free, and relatively easy to find.

K x