imaginary friend. I moved to Cardiff from Hampshire 9 years ago with dh's job. We really thought it was lovely but thought we'd miss the south east and only be here for 2 years. 9 years later we LOVE it. It is totally our home now and we cant imagine living anywhere else. It grows on you really quickly. Yes, to start with you do have to get used to the place, the people, culture, the fact that it is in Wales etc. but then you'd get most of that if you moved to say the North East or anywhere really proud of their heritage. Very quickly you get used to the in-jokes, funny local sayings and the like and become truly at home. I've only had a few problems with being English and often because people thought I was being negative to the welsh. People know I'm english and aren't concerned. I've had two children here and I consider them English, until they decide they whether they feel welsh or english themselves.
I live in North Cardiff (Rhiwbina) and a fair few of dd's school friends parents are english too. The schools are fantastic this way (Rhiwbina is between Whitchurch and Thornhill both areas other people have mentioned too). All those areas have a train into Cardiff City Centre (not far from university) and regular bus services. Taxis are cheap too!
What you will find is that people here are really friendly,much much more so than the south east. I often go back home to Basingstoke and chat to people in the shopping queue's like a do here and they look at me like I've gone off! Here everyone chats away (particularly when you have children with you!).
Nights out are fab in Cardiff too, the city centre is very safe and great for nights out, restaurants, bars etc. Unlike the South East, all ages of adults go out, so you get people out partying with their grannies and having a great time.
The only thing I find at all negative about Cardiff is the distance it is from family back home and having to pay £4.90 for the bridge every time, but otherwise its great.
It has loads of parks, fantastic shopping (and they're building a huge new mall at the moment too), great entertainment (stadium, millenium centre, theatre, tons of cinemas) and very easy to get out of Cardiff to the Brecon Beacons or to the Gower (both about an hour away so great for day trips)
You will find cost of living much cheaper then London. Transport, restuarants, pubs etc all much cheaper.
Primary school are different to England in that they have their nursery schools on site. They are always seperate buildings and play areas from the primary school. I was a little worried about this at first but they are really very seperate and not at all school like and also, they really help the transition from nursery to reception class as they just go to a different area of the same school and all their friends go with them.
Let me know if you have any other questions. I have lived in St. Mellons (dont do it); Penylan (near the Roath end) and Rhiwbina so know a lot about different areas and schools.
Cardiff is fab, I love it!