Hi I'm new to this forum and looking for some advice, I went to check my coolant level today and noticed the top radiator hose was flat, I took off the radiator cap and the air rushed in and the hose went back to its normal round shape, is this something i should be overly concerned about..?

I had this problem before. Rectified it by buying a new radiator cap. Apparently theres 2 types and I had the wrong one.

EDIT: Thread here: http://www.aussiemagna.com/forums/showthread.php?t=68417

Apparently the CPC brand caps are crap, thats what I had. Got another $20(? was a few years ago) one from Repco and problem solved.

The problem is not always the radiator cap - if the hose that goes to the overflow tank is blocked, or the overflow tank in/outlet has crap in it the coolant will not flow back to the radiator when it cools. Generally if it is the fault of the cap it will be due to the small return valve in the centre of the cap getting blocked with rust etc.....sometime you can clean this but generally a replacement is required.
The correct CPC cap for your car is 580-90. I've never had any problems with CPC caps which are standard equipment on most Australian built cars. They are also exported to many countries so they cannot be that bad.

Guys,
Thanks so much for the quick feedback I will check these out tomorrow..

Also worth noting that Repco caps are actually made by CPC...

Not the radiator cap, is generally the overflow bottle hose is blocked in the actual bottle. Is again one of those common things as the pipe on the bottle has a brass sleeve which means there is a very small opening, get some gunk in there and then it is all over

I only use genuine caps BTW, a lot of the aftermarket caps are rubbish and can cause more issues and CPC are one of them in my opinion, Mits used ND caps which is what I also use