The card fee is hardly hidden away given that it appears right next to the amount you have to pay!
From the payment screen:
amount:
(plus handling fee of GBP 4.95/EUR7.45
for Visa and Mastercard payments and
GBP 1.00/1.50 EUR for Switch/Maestro
or Visa Debit card payments, if applicable.
You can avoid paying this fee by using a
Solo or Electron card.)