"I just get a blocked nostril now and again and it jumps sides, very odd."
Oh I used to get this all the time, it might not be sinusitis so much as trapped fluid or air in the sinuses, ie no infection, but the sinuses still have the pressure. It was worse for me in bed, I'd roll over and I'd feel one nostril clear all of a sudden and a few minutes later the other one's blocked, it's really kind of weird like that

"Tonight my nose was running abit, was clear though."
Yeah that suggests more of an allergy, which will block things up anyway and can also affect your sinuses. Though having said this when I'm at my worst, I'll often spend ages sneezing and blowing out clear fluid, this only affected me at night though, just before bed so I suspect it was dust more than pollen etc.