Mrs LoM had something similar recently and was referred by the GP to the ENT unit at Barts where a comprehensive dewaxing seemed to sort things out.
Around 15 years ago I caught an ear infection while skiing at altitude in Breckenridge Colorado and had intense pain on the drive and descent into Denver. My ears then started bleeding on board the plane, but at least the pain had gone by then. It took around 3 weeks with 2 types of antibiotic treatments to clear the infection and hear normally again. My ears are now very susceptible to infection if they get the least bit damp.