Thanks guys,
I've just looked at my current standard filter, its not a panel, its a cone / round one.
So i'm guessing i would need one like this..?
http://www.ebay.co.u...=item4837903321
Can i just leave the top of the box off..? or will that do bad stuff to my engine?

I have more or less the same one on my 1.8 tdci and ive replaced it with a pipercross cone, this is all contained like standard inside the factory air box.
its more for performance as i have a remap and tbh the intake sound on a diesel doesnt sound that good.
in theory you could take the top of the airbox and leave the filter in aslong as its properly secured the only point of the filter is to stop particles being sucked in, the factory airbox is designed to quite down the intake along with other things, and tbh in my experiance there isnt much noise difference between aftermarket filters, you'll only hear the intake sound properly under medium to hard acceleration.
im unsure myself if i wannt to just go for a simple cone filter or go for a full induction kit with a cold air feed built into the bottom grill.
If you have the money the full induction kit will be best and as artscot says a heat shield of some sort would help.