I think you might have a slightly overly optimistic view of British seaside villages!:-)
Seaside Villages in Cornwall and Wales are quite different in appearance so it might be worth doing a bit more research to identify what type of atmosphere you are looking for.
What you will find will vary depending on when you choose to visit. Popular seaside towns can be quite dead and closed up in the winter, and very busy, full of tourists, in the summer.
If you don't drive you will be limited by the availability of public transport . Public transport will generally only be available to the more popular, therefore busy, locations.
Tenby is a good suggestion, but again it definitely isn't quiet during the holiday season.
Regarding "getting to know the people of the villages", again this might be slightly optimistic. Why would they want to get to know you?! I say this as someone who was brought up in a tourist town. Don't get me wrong people will be friendly, kind, helpful etc but don't expect to build a relationship with all the "colourful locals". You will be just one of many that walks their village every year.
If you do choose to visit north wales be aware that the first language in many of the villages is Welsh. People do speak English but the chat you will hear in pubs, shops etc will be in Welsh, which will limit opportunities for interaction. Some people interpret this as rudeness/standoffishness. It isn't, but it can be a little offfputting to a visitor.
Another area worth looking at is Yorkshire. There are some lovely seaside towns and villages up there,.