Hi Jules26. Welcome to the forum.

I am not a doctor.

I am a chronic sinus sufferer and the last couple of months have been terrible. I think it's the unseasonable weather.

Here is what I find relieves my symptoms.  Buy a cheap facial sauna from Argos. Buy a bottle of de-ionised water from a supermarket or garage.  Boil some water in the sauna and breathe the steam for about 10 minutes, two or three times per day.   I also put a small pad of kitchen towel inside the sauna hood, and put 2 drops of SuperDrug decongestant drops on the pad, then breathe the steam and fumes. The steam evaporates the drops and you get a big hit.  Don't be a hero because the effect is very strong, and you don't need to breathe a lot of the fumes.  It should loosen the mucus and allow it to drip out of your nose - if you can get a sneeze going, so much the better.

Try this for at least a week and you might have to do this every day while this weather lasts.