Ah-ha! Well, these are a *lot* like the Hamish Macbeth mysteries, but set in North Wales instead of Scotland, in an imaginary town called Llanfair*, which seems to be in between Conwy and Caernarfon, and Constable Evans keeps going to Llandudno, Colwyn Bay, Prestatyn, and so on, which is wonderful beyond all reason.
This one was set around an Eisteddfod at Harlech.
PS. I pay absolutley no attention to the plots of these, so I haven't got a clue if it's a good mystery.
* Definitely not Llanfairpwllgwyngychgogerychwyrndrobwllllantisiliogogogoch.