Yes, there's loads of stones in Cymru waiting to be found (there just has to be). For micro-cups have a look at the stone found on Holy Island (search above for 'Lindisfarne'). That stone has been handled and identified by Stan Beckensall, who's like the father of UK rock art.

Here are the grid refs Blossom .
SH 69393 73132
SH 69428 73070
SH 69586 73362
When converted to Lat/Long
53.2391025335215 -3.95848912164206
53.2385541673024 -3.95793958250884
53.2412162216371 -3.95569326591673

copy and paste into GE and you can see the main rock quite clearly the other two are smaller .