If you deposited by Credit Card then you can try and ask for a refund on the grounds they're banned from gambling in the UK.
If by bank transfer, bitcoin or other dodgy payment methods, there's nothing you can do.
The site is a scam, you won't get anything back from them so don't worry about them blocking your e-mail.
If by debit card, you can ask under the grounds the casino wasn't licensed to take your money, it was an unregulated transaction contrary to UK laws and they have only refunded part of what they should have done.
Trouble is, they are confidence tricksters and WILL pay a bit when it suits them, usually if they sense a big depositor or problem gambler who is almost certain to make them a profit in due course. The refund is their 'insurance' in cases like yours, so they can say they did pay some back and insulate themselves from most chargebacks if you claim the dposits were fraudulent. They know exactly what they are doing, by now some East European will be driving around in the Cyrpiot sunshine spending your dosh having channeled it through 2 or 3 Panamian and Caribbean bank accounts.