Although the OP was clearly breaking the rules by opening multiple accounts and is a citizen of the UK, I strongly believe that sportsbet.io should return the deposits as an act of goodwill. 12+ BTC is a lot of money. I think it is a bit heavy handed for the infractions committed by the OP. I especially hold this view since it appears that the OP provided his real documents to demonstrate that he was a UK citizen. This indicates to me a careless ignorance of the rule against a UK citizen playing on their site, rather than deliberate fraud. Unfortunately, the creation of multiple accounts to override a betting cap was definitely not on the up and up on the OPs part.  Also, I agree that the OP should move this to scam accusations.
BTW,  If the OP wants to get representation on this matter to help him recoup his funds, I would not recommend that he use game-protect's services. I'm certain he can find much better representation than what game-protect will provide.