Relatively new here, but I can add to this. Moved from London to Plymouth just over a year ago, not to retire but a change in employment. Got sick of the unrealistic workload expectations my place in London was wanting, along with the massive commute on delayed, expensive trains, so started looking for another job and ended up in Plymouth, which I wasn't expecting. Massive increase in quality of life, much larger house for less money, with parking so I now have my weekend sports car. Commute is now a 25 minute walk so guaranteed knowledge of when I am going to get to work and get home.
When looking for a place, I considered a few of the towns around Plymouth, and even looked at Exeter, but being able to walk to work was a big draw. Ended up settling in one of the nicer parts of Plymouth just north of the city, away from the students and in among the what my work colleagues call 'the posh bit'. I don't have an issue with Plymouth, and it isn't as bad as people were telling me prior to going there, although a few kept confusing it with Portsmouth. There are parts were I wouldn't want to live, either due to being a bit rougher or the massive influx of students meaning your neighbours change yearly, but there are undesirable parts in many cities in the UK. The other added bonus is that I see the sea daily, and can get down to the Barbican or the Hoe in 15 minutes, and on a nice day it is unbeatable.