Questions about ISA transfer timing

I have a fixed term cash ISA that’s expiring next month, which I want to move to a Trading 212 Cash ISA.

First of all, it appears that it’s not possible to transfer a Cash ISA to Trading 212, but it is possible to transfer the Cash ISA from another bank to a Trading212 S&S ISA, and then in the next step it would be possible to transfer it from the T212 S&S ISA to a T212 Cash ISA. So that’s what I’m intending to do.

But my maturity is on the 13th September so in about 1 months time. And the interest rate is higher than 5.2% so I’d like to keep the money in the old ISA for as long as possible. Is it possible at all to give T212 instructions to transfer the ISA only on the day when the the old ISA matures?