How can I REMOVE Gmail from my Mac Mail

Since I've had the new iMac (Mountain Lion 10.8.3) I have this annoying Gmail set of the same mail boxes as the 'normal' mail list. I've tried to remove/delete the whole lot, but it won't allow me to.

I don't want Gmail at all because here in the UK we have 'Virgin Media' which is probably the best ISP available. Apple support said it is not possible to remove from the Mac Mail window, but surely there must be a way to remove something I never installed myself and never wanted. I've seen that it's also to do with IMAP - which I do not want either.

Can anyone please tell me how to remove it completely? Here's a shot of the problem:-