I really liked Floss's character. She had great warmth about her but I can understand why Colleen and Celia were better fitted characters. They brought something different to the show as we already had Pippa and Ailsa as warm motherly characters. Celia and Colleen could bring more comedy, also Celia and Colleen could stir up trouble with their gossiping about people. Celia and Colleen could be quite nasty at times.
I think Celia's character had more room for development and had potential but Fiona Space decided to leave.
If Fiona Space had stayed long term I think Celia would have had mostly Colleen's storyline’s and eventually work in the diner like Colleen. I'd say Colleen probably wouldn’t be brought back as a regular if Celia had stuck around.