If you're going to leave the scope out in the obs it'd be better to lay a blanket or something that absorbs moisture over it Kev: even then I wouldn't leave it completely un-checked for 3 months.
Plastic bags will trap moisture...removing it from the primary & inside face of the corrector is quite easy (more so if you can just position the ota when you have a GEM like us) by positioning the ota upright (or as near you can in your CPC, ie the corrector end face-down as far as possible) & removing any after-market focuser or attachments to to rear thread of said scope.
I place a single layer of a Kleenex tissue (ie, peeled) over the open focuser end & secure it with a rubber band just to keep dust etc out then crank up the heating in the room it is in & leave it like that for a day...usually dries the inside out bone-dry.
Megiddo has a good ploy - you can simply stuff a few packs of silica gel into the leg of a stretched stocking & gently push this down the baffle tube until it hangs out the other end (look in at the corrector end to see the progress) & then tie off the other end of the stocking to something (eg, the primary knob) & use a rubber band & plastic bag to seal the end you inserted this device into.
As said these ota's are most certainly not airtight but hanging some gel-packs inside does keep moisture condensation at bay for some time...I've used the stocking trick a couple of times but because I can separate the ota from my mount easily I prefer to keep my C14 inside with the corrector face down on the floor in a dry environment.
I wouldn't recommend cycling your scope through heavy condensation cycles too often btw although we've had to deal with it on numerous occasions such as unexpected rain like another poster here, as well heavy moisture ingress when we pumped air through the ota to cool it that way - why we now use ice & keep our rear vents sealed...but I guess that in Eire you don't have the temperature equilibrium issues we encounter here so markedly...