Can the fee charged be increased to cover the charge of changing currency for service providers in other Member States?
With online card payments you price in sterling and you get paid the amount charged in sterling by the card provider. You will typically pay a higher fee for overseas debit cards. You cannot charge applicants from other EU states more than UK-based applicants, so you should factor the cost of accepting those cards in setting your fees. You will be able to get the precise fees from your bank and payment service providers.