And Gareth Thomas....
Standard English schools in Cardiff go like this IMHO
Cardiff High - regularly rated best school in wales
Gap
Radyr - excellent school, may be issues with catchment once new massive housing estate is built by it.
Smallish gap
Whitchurch - largest school in Cardiff. Can usually get in outside of catchment. Especially good for sports
Smallish gap
Llanishen - good school sometimes switching places with Whitchurch. Results can suffer some of the less well off areas get put into this school and have to travel 4 miles in due to Cardiff High catchment and parents desperate not to have their kids go to more local schools of Cathays and Eastern high which are both in the bottom of Cardiff schools.
Bigger gap
Fitzalan - improving all the time was once not to be recommended but has had a few steady years of improvement.
Then the rest are below the national average and pretty dire compared to the others.
I think Whitchurch and Llanishen are pretty much the leafy subs you want to avoid. Especially Llanishen where the action is centred around 3 nice streets and the pubs/cafe are average. Penylan, Pontcanna and Canton might be closer to the action for you with a large mix of pubs/cafes and art, entertainment venues.
But you can get to the centre anywhere in Cardiff in 15 mins. Both Whitchurch and Llanishen have trains 2-4 times an hour which take no time to get into town.