They are not losing all of it I would say. Basically if a gambler is fond enough with a site, it will not be much hassle for him to access it through a proxy. However as a unlicensed gambling site, the risk are far greater than keep on serving business for the UK customer .
It will be much of a nightmare for you because you might see the legal feds knocking on your front the next morning and this would be the reason that most unlicensed sites has taken the safety precautions rather than facing the law in the future
Why would a gambler continue to bet with a site that still hasn't offered a full explanation of the situation?
If they are willing to ban one country's IP with no explanation, they will continue to do the same with other countries sooner or later.
Their business is finished.
Actually there is already an explanation for all of this , it will be because they are unlicensed and there is a risk that they might be taken down. So if you ask them, they will explain to you that online gambling is illegal there and so on rather than telling you the truth about that they are unlicensed and not banning the UK IP will harm their business
Not every country has a great influence towards online gambling, which in this case UK has some influence I would say that most sites has obey their request. If only the request coming from some country in the middle of Africa, I doubt that they will follow the request