Difficult to become self clearing here in the USA. Too much paperwork time legal difficult to get approved.
You need to have a broker dealer license in the UK and be cleared by the Financial Conduct Authority or FCA. Which is the equivalent of the SEC and reports only to the Bank of England. You need a lot of cash lets just say no less than 7 digits to back any shorts or longs you put into play as a self clearing "intermediary" which is what a brojer is called in the UK