Doesn't the payment information page have a litte * next to worldpay and the words See Surcharge Fee Note Above. written underneath ?

You can also change the words in Admin using SURCHARGE Payment Description (HTML) so you could change it to Surcharge on worldpay payments only or something similar. Other than that, you should probably contact the original author of the module, because I think that it is exactly the correct place for surcharge information to appear.