I am a previous Londoner who moved to Swansea 20 years ago. So I know it pretty well!
It sounds like it is just the two of you?
We chose Uplands, which is urban, diverse and lively, studenty but areas vary. Lots of beautiful streets, many with gorgeous sea views. Beautiful Victorian parks and an easy walk to beach and the town (which is rubbish!). A small centre, with some nice bars and eateries and a small tescos and Sainsburys, plus a post office and lots of coffee shops. Plus a monthly market. It has a lovely community vibe. Students are a downside for some - we like the energy they bring, but don’t live in a particularly studenty road. And yes, they definitely do impact on rubbish, plus lots of HMOs which are not attractive. So pros and cons but we have lived here for 14 years and love it.
Sketty is more upmarket and also has a small shopping area. It is more middle class really, and quieter. It’s a bit more expensive - we really like it. Derwen fawr, albeit part of Sketty, is more surburban. It is very popular, but we found it lacking in diversity and, well, it wasn’t for us. I like the area on the hill around Sketty primary, and also Tycoch too. Sketty park is largely a council estate and I don’t know it well.
Commute to Morriston is fine.
Further West you have Killay and Dunvant, which are decent, quiet and safe but less facilities. Killay has a nice shopping area but older demographic. And then down on the front, you have Mumbles, with Mayals and West Cross on route to Mumbles.
Mumbles is very pretty, glorious beaches and access to Gower, lovely gift shops, surfy shops, deli, M and S food etc. plus lots of coffee shops, restaurants and bars. So popular for good reasons. We rejected it due to travel, particularly in the summer when the one road in and out is often congested and less for your money. I do like it though.
Running and fitness is very popular. We have park run on the front and various running groups. Swansea has a 10k, half marathon and various trail running events. (Google Darth Mannion Gower if you are hardcore)! There are lots of year round sea swimming groups and some great gyms - you will be amazed at the price if you are used to London gyms.
I have made loads of friends and I love it here. The only thing I don’t like is the crap shopping - we have some shopping parks etc, but we always go to Cardiff for proper shopping.
it is a small price to play for the parks, beaches, people and lifestyle. You will have to learn to love the weather! Good luck!