I use orthotics, the type with the rigid plastic arch support. Yes, Vit D is very importab=nt too, you can buy a Vit D test that is a prick test from the NHS on Amazon if your GP is not helpful.
You can use a frozen plastic bottle with water to roll in your instep, and also stretching by massaging the insoles with a ball (tennis size or smaller).
I also have supportive socks for when it is bad. The insoles are for all day every day, not just when riding. I found Cranio helped, but a friend was also helped with accupuncture. I did not find physio helped.
