In reply to alex_th:
I have broad feet and finding boots that fit is often a challenge. SImply buying a larger size just means they don't fit in a different place. Your feet may have got flatter, as the ligaments can stretch with age.
I once bought a pair of boots which seemed fine to begin with but by the end of the day were cripplingly tight. I went back to the shop for advice and they suggested my feet were pronating when they got tired. They recommended Superfeet to support the arches and tongue depressors*, which did the trick. Probably worth a try, and a lot cheaper than new boots.
*not the giant lolly stick a doctor uses to inspect your tonsils, but shaped pieces of hard foam which fit between the laces and the tongue of the boot to help seat your foot in the boot properly.