Polly,
Exactly the same thing happened with my ZUF270 a few months ago. I called a local repair company and they fitted a new element, something that I think is easy to do youself. It took the guy five minutes to do. I think it is just a case of unnscrewing the panel at the back of the oven, then unscrewing the element and fitting the new one.
The problem is that 3 months later, the same problem occurred again. The company returned and replaced the element again, free of charge but yesterday it happened for the 3rd time and only a month since the last element was fitted.
I'm now wondering whether there could be a manufacturing fault with the oven. I'll contact Zanussi but I think that companies are reluctant to admit there's a problem unless they've received lots of similar complaints. The other possibility is that I've managed to find a company that fits dodgy parts. I'll let you know how I get on.
Gary Thomas, January 2009