Modern and Regency

Thanks for asking. I must agree with you on the quality of many published sequels. Some are well done but certainly not all. I also really enjoy the creativity of many authors here. I don't always love the direction an author has taken but many AU's (alternate universes) are fun to read and stay very true to the characters. A chance to scroll down the archives and share what I loved is always a great opportunity! :-) I won't repeat any stories already listed (I think).

My favourite modern story is an older one but I completely love it - Museums and Misunderstandings by Kate F. You can find it in the epilogue abby. It's primarily P&P but characters from other books sneak in.

For Regency stuff, I really like Lise's Persuasion stories. Many of them feature Admiral and Mrs. Croft and have lots of humour.
I also really, really enjoyed Love Suffers Long And Is Kind by Susan K and Laura Louise (also Persuasion and alternate couple but VERY well done).

Try Suzanne O and Sarah Waldcock's stories. Both are great writers and they complete their stories. I would also suggest Janet and Elizabeth by Tamsin (AU but very good and believable).

I liked EVERYTHING by Mags (who doesn't seem to be writing any longer, more's the pity). She mostly wrote Northanger Abby fics. Her story, The Firstborn, is an intersection between Northanger Abby and P&P and is an excellent read.

I also liked An Amiable Man by Judy-Lynne (Bingley-centric).

I hope you give them a try - happy reading!