Critch, what type of flying are you doing at the moment?
The reason why I ask is because during my PPL and CPL training, if I ever flew with a slight cold (I know they say you shouldn't)!! I never experienced any problems with my nose in the descents simply because we didn't go high enough. We used to go up to about 3000 - 4000 feet.
However, when I did my IR training I once flew with a cold and in the descent down from FL90 my sinuses gave me so much grief that I had to hand control over to my instructor because I was in so much agony. My eyes were watering and my sinuses were giving out shooting pains.
This really brought home the saying "Never fly with a cold" because until that day I'd never really seen it as a problem.
So, if your sinuses are just temp inflamed then FlyingD is right, you just wouldn't fly for a few days. I hope this is the case for you and that you'll be soon back on your feet/in the air!
PS: I find the Becanase nasal spray works quite well on the odd occasion that I have to use it, and my AME doesn't mind me using it either. There's also one called Otrivine that I've heard mentioned on here before but I don't know if that's one of the CAA-approved sprays or not.
Good luck!
MB