Coral Casino - Self Exclusion

I recently opened an account with Coral and played the casino slots, winning £74,000 (£74k). Having submitted a withdrawal request my account was frozen the next day. I contacted Coral to find out why and was told that the account had been self excluded 4 years ago in September 2011 and that the winnings would be withheld. I genuinely have no recollection of this. I asked Coral to investigate further and received an email saying that I have had 'several' GalaCoral accounts (wasn't aware Coral and Gala were linked) and that I had tried to circumvent the system and that while my deposit would be returned, i would not receive the winnings and that is the end of the matter.
Firstly, I have made no attempt to circumvent the system. Coral confirmed that my name, email address, and phone number were all identical. I also believe the password used would have been an exact match. The only change is my address as I moved 3 years ago. Secondly, Coral confirmed that their policy is to return all deposits (win or lose) when duplicate accounts are set up. If this is the case, then why haven't my deposits from the 'several' accounts been returned?
Whichever way this is cut I believe that Coral (GalaCoral) have very poor account matching to prevent players from opening multiple accounts and that they happily take bets which lose, but fail to honour winning bets.
I have requested proof that the Coral account was self-excluded and have had no response.
I would like to take the matter further, but not too sure how.
Any advice or help would be greatly appreciated.
Thanks,
Matt