There is a certain amount of character change, with a background of very long-running characters. Sophie is an original character, I gather, and Dani has been in it since childhood. I've only been watching it since starting with SSiW (which I think is maybe a year, 18 months after SSiW got started). I've seen a few old episodes on Youtube, and you can see people like Dani, and Mr Lloyd when they were younger, and I think there is one where Terry and Glenda got married, for example.
Your comment about Vince and Lowri is very perceptive, because they had a flirtation once before (probably at least a couple of years ago). However, it came out before it had developed into an actual affair. Lowri and "Kelv" made it up (and the result was Mia! ).
But now...who knows...?