As of April 14th 2020, UK customers will be banned from gambling with credit cards due to new regulations. This applies to all operators and all forms of gambling, thus meaning that you'll not be able to make any deposits with a credit card or with an eWallet (PayPal, ApplePay etc) if you fund it via a credit card.
You can still deposit using debit cards, prepaid cards only if they are not issued by a Money Service Business (you won’t be able to deposit to your account using N26, Transferwise, and Post Office Travel Card).
In most cases you can still withdraw back to a credit card already registered on your account if that's how you've deposited in the past. Please note you will not be able to register a new credit card.