Reformat, get an authenticator (UK allows that right?), and blizz should help you recover your account when you provide the right information.

A word of caution though be careful about using unknown "anti-malware/adware scanners" as they often throw a false alert at you and then you give it UAC permission to install the "fix" which may indeed be the trojan that steals your info.

I finally figured out that was how I got scammed a while back. Had a fake adaware message pop up and totally fell for it. Sadly I work with network security on a near daily basis and even I was a click happy victim.

Good luck, if this is the first time this happened to you odds are you'll get most of your stuff back in a few days.