A couple of suggestions, Zeeland, in the Netherlands. Just North of Zeebrugge, through the tunnel. Loads of lovely little towns and villages. Upmarket seaside towns, loads of accomodation, and places to eat. It’s flat though, so may not suit all, but my OH loved it. I can recommend a B+B in Renesse if wanted.
Then, around Flanders, anywhere in a triangle of Ghent, Brussels and Roubaiux. We were there last year for a Sportive, it was excellent. Loads of small hills, loads of cobbled roads and loads of lovely cheap beer in each village.
I think Belgium is very under rated for a short break holiday. We try to go at least once a year, and thoroughly enjoy it every year.