Well, after a few days wondering why there was a 'wet' patch on my drive when it hasnt rained for a few days i decided to take a look to make sure everything was in order.

Opened up the bonnet and there was no oil filler cap. No idea where its gone, theres plenty of possible explanations to why its decided to leave the car but thats not really going to help.

Really i just need to know is how much its going to cost me and what i should do in the mean time. Do dealers keep them in stock? Anyone had this problem before?

Ring your dealer and get them to get one for you and deliver it if at all possible. Failing that if you can secure a piece of thick polythene over the hole (cable tie) so you can drive to get it. Thats what i would do, hopefully the first option.

Only about a fiver mate depends on your engine size?