Has your GF checked with her bank to see if the payment has been either denied or processed through?
WorldPay is the secure payment side of WorldBridge, and as such, WorldBridge, per UKBA, is the contact point. I promise you they want that money! The contact you made with WorldPay earlier today is good-they are checking into the error message your GF got, but you might have her contact the email address for WorldBridge too.
She should check the bank to see if payment has been denied or processed, attach a screen shot or PDF of the error message, the information that contact has been made with WorldPay who say they are looking into it, and include her application number and the result of her checking the bank info.
WorldBridge telephone line is indeed a hideously priced premium line, and I've not read one post saying it was worth the money for the 'assistance' gained during the call. Most people here have reported being put on hold for long periods of time (whilst the meter ran) and ultimately didn't get any real answers.
Check the bank and then email WorldBridge; hopefully WorldPay will be contacting your GF soon with results from their looking into the problem, too.