Hi Stilton,
occassionally have sinus blockage/infection issues, also broken noe/sceptum etc. But, one time had a 3 week headache that all painkillers failed to touch. Works nurse recommended that it was sinus infection/blockage causing pressure. His advice was to find a liquid decongestant like the 'Vicks' bottle spray (squeeze the bottle and it atomizes into the nose. Use the normal 2 squirts or whatever the bottle recomends. Then, lie on a bed and allow your head to hang over the end, i.e. so the liquid can 'run' up inside the nose and directly affect the sinus, this will sting like buggery. Then after a few minutes sit up and if all goes well the Vicks will act directly on whatever is 'blocking' the exit of the sinus and start to clear it (whereas atomising up into the nose in the normal way, most of the liquid hits the inside of the nostril and runs out again, this way you get a direct hit on the sinus) and hopefully you will feel the effect almost immediately.
My 3 week headache went completely in 30 mins! Good Luck.
Brgd's
N1 Vibes