Audax is a good shout. Also try typing the name of a town or area into google along with sportive. There are so many of the things there will be one nearby. Did a lovely ride in Scotland yesterday that I found this way.
The other option is strava. A bit less easy. But if you go to segment explore and pick on some segments in the area you want to ride you can look at the leaderboard, open up some rides and see where the locals are riding. Doing this at he weekend. Morning of a wedding, opened up the segment going past the BandB so will be following someone elses ride. Risk here is that they are some sadistic machine who hits all the worst bits of road as training!