I suspect these 'credit' cards are actually debit cards, which work in the exact same way, albeit you need to have the funds loaded up first. They tend not to actually give you any 'credit' so there's no chance of building up debt, if that's your concern.
Er, Revolut IS a pre-pay (hence debit) as I said.
Saves the hassle/potential credit history implications of applying for a fee free credit:
https://www.money.co.uk/credit-cards/credit-cards-with-no-foreign-transaction-fees.htm