I'd get him to the vet directly. It sounds to me as if he's got a dose of cat flu - which is a nasty beast and not at all just like a bad cold. He should have been vaccinated against the main threats long ago in any case. (And while you're there, get him microchipped, particularly as he goes outside.)
one of "my boys" shakes his head a lot and when he does slobber/snot flies around he is well in himself doing all his normal catty things.i couldn't tell you if he has always done this but ive noticed it recently<last few weeks> when he has sat on my lap and ive been splattered
he is not fond of the vets and I just wondered if anyone has any advice-should I be worried?