We are not a bank and don't take risks with your money by lending it out or re-investing it. That's why your account doesn't need to be underwritten by FSCS. Instead, we keep your funds in segregated accounts governed by the e-money regulations of the Financial Conduct Authority.
That's the same system used, for example, by the PayPal wallet, Transferwise, and Revolut. In the exceptional event of any default on our part (or any of our Partners), 100% of the money you have paid in would be returned to you directly from these accounts.