I've experienced the same thing intermittently (I'm in the U.S.). After testing, my Dr. attributes the very real symptom to a nasal spray (prescription cortisone) that I use to control sinus infections. Additionally, said Dr. says the sinusitis is caused by my profession (pilot) which induces the infections because of dry air (pressurized airplanes) and the constant irritation of the mucous membrane lining of the sinus due to pressure changes.
I've also noticed a slight but distinct loss of sense of taste... but, again, Dr. says loss or change sense of smell usually correlates to loss of sense of taste since they're so closly related.
For now, I'm just marking time and still using the nasal spray since it's only used about once a week once a day. I'd say nearly 60% of those I come in contact in my profession have greater or less problems with sinusitis and nearly all occasionally describe your (and my) phantom smell sysmptoms...