Thanks for the replies and I hope everything is going ok with you SAS!
I managed an appointment today and basically as Bob says, doctor thinks the eustachian tube is blocked, the ear drums were ok, no wax issues, so its the middle ear. A course of antibiotics to cover any infection and some nasal spray to help unblock the eustachian tube, although my nasal passages were never blocked.
He advised me to regularly try the pinching/blowing technique, swallowing and steaming to help unblock the eustachian tube, if thats the cause.