I had this issue before, super easy fix.
Go to Halfords or local motor factor, purchase an Air Conditioning Cleaner Gas Bomb, start car, set fans to recirculate, put passenger seat all the way back, activate bomb and place in passenger footwell, exit vehicle, wait...wait.....have a cuppa....wait some more, after about 30 mins, shut off car and open doors to air out gas (make sure no new lifeforms enter vehicle while doors are open)
Job done