Most of my rides are in the 30-60 mile range, and I rarely average more than 13mph, usually on a chunky Croix de Fer.
I did some longer rides, and in June did 100 miles at 11.8 mph.
When I did RideLondon in 2022, I used the faster Allez, and managed about 19 mph. Had very little training but was lighter. Don't think I could do that now.
(Both speeds are based on moving time, not elapsed).
Will be trying a 250mile audax in May. Haven't ever attempted such a distance before. Not sure if I'll finish within the time limit!