So what happened to the VPN afterwards? That's exactly how you're supposed to get yourself out of this. Secondly, you played in the UK should possibly mean you were in the UK when you got registered, but not with credentials from the same location right?
First of all, you're talking about selling an account that already bears your initial kyc documents? Look, you're just trying to cook this whole thing up in a way that you'll never be able to recover that funds, ever again. Is there something you're not telling us about the account?

Yes, I think that should be the most preferable option to do right now at the moment, by moving to an unrestricted country such as Russia, Norway, Finland, Poland or Slovakia, and complete the KYC so you can have given access to your fund and withdraw it, rather than trying to play smart and gets your account terminated if you happens to use VPN, as it's against it's rules.  Because I actually noticed that UK is actually among it's list of restricted countries by BC.Game casino, of which I'm pretty sure could be as a result of unfavorable licensing law. Or, how about you contact any trust worthy Russians on this forum and discuss percentage that you will give him/her if the person helps you complete KYC and have access to withdraw the funds. Because I'm pretty sure there will be people willing to assist you, but only for a cost.

This  is why it's necessary to know or read terms of service before  dealing with any of these casino platforms and what they will require of you. Firstly you should try to know their terms of KYCing, if they're going to ask you to do your KYC in the future or when you must have reached a certain threshold. Now without the KYC at this point, your funds  most likely have stocked up.