Freetrade, the UK challenger stockbroker, completes $15M Series A

According to a US based equivalent Robinhood [1] they make a significant portion of their funds from "uninvested cash that isn't swept to our network of program banks. We do this primarily by depositing cash in interest-bearing bank accounts outside of Robinhood Financial."

Do companies like this fall into any of the same regulations that normal bank/financial institutions require? Is there a big fractional reserve held by these companies somewhere that needs to represent their client's uninvested money?

1 - https://robinhood.com/support/articles/360001226106/how-robi...