Bestinvest says
This facility allows you to hold cash within an ISA for a temporary period. The money must be destined for eventual investment, but in the meantime you can review your investment choices without the concern of immediately committing to a specific fund - particularly useful if one needs to utilise their annual ISA allowance but the tax year deadline is looming. For deposits not held within the ISA wrapper depositors can use the CoFunds Cash Account.
This cash account is effectively a deposit account is designed to allow investors to hold money destined for investment on the Cofunds platform. The underlying holding banks are Royal Bank of Scotland and Scottish Widows Bank.