Nigel and Stuart at Hart events Monmouth should be able to meet your requirements, both Welsh international shots. Julie makes lovely cake too.
Treetops can be good when they get it right but in my experience that's not very often.
South Wales 2000 though mostly trap orientated do put on a good sporting and compak layout also the owner is a shooter so has some enthusiasm towards the sport not just making money, the welcome is friendly too. Also a proper on site cafe.
Not been there myself but as others have suggested Woodland park is said to be a nice ground though you can only shoot their sub sonic cartridges there.
There is also Crynant shooting ground. Based on experience I strongly suggest you don't bother.
As Will suggests Mid Wales shooting centre is a good set up. Like South Wales 2000 mostly trap orientated though they do offer good sporting layouts set in some beautiful countryside. As the name suggests though it's not in South Wales ., approx 2hrs of twisty country roads away from Cardiff but If your prepared to travel that far then Griffin Lloyd is also a good ground set in truly stunning scenery.