Droogs
Not the Sharpest Moderator in the box
Simple, make it also illegal for a mainland domiciled person to own an off-shore limited company, you can only invest in PLCs. ~If you live here then be registered here for your business activities and pay UK tax. Any overseas earnings from foreign companies registered in known tax havens are taxed at 70% and anything bought with money held overseas has the 200% JRM Britannia Jingoist Git Tax applied to it. Also MPs must give up all holdings in non UK companies within 60 days of being elected. If you are Joe Bloggs then you get 90 days to sort your affairs and bring the cash home for proper taxation.Singapore don't allow dual citizenship, if you want to be part of their country, you commit to it.
People would find a way round the £15k limit, for example form a limited company in the Cayman Islands, and loan it lots of your money, then it's technically the company's not your private money.
I have an offshore bank account that I still use since it has a sort code, when I sell my property I'll instantly become a criminal and have all my money forfeited... unless there's a rule allowing certain situations, which will then need adjusting as more problems are found, and then people use those changes as loopholes.
The whole point of the act is to stop the gits that shafted and lied to us from making any profit from it