Is Cardiff closed to GA?
The notam doesn't say anything about that. It says flying club is not available (presumably closed?) and mandatory handling via Signature.
Is there more than 1 handling agent? If not,
mandatory handling is illegal under EU law.
I've been to Caernarfon a few times and really liked it. Fantastic location. Watch out for the fog, and once you hit the town don't worry too much about the millions of pregnant 14 year old girls pushing prams - that's Wales for you; Welshpool is the same