Re: Not got much hope
MVNO operator giffgaff has recently rolled out a 2nd-factor protection against SIM swap fraud. They send a code as an SMS to the existing SIM and as an email to the registered email address, so you have to have one or the other to be able to carry out a SIM swap.
I recently tested this when I lent my mother-in-law a SIM to use while waiting airside at Heathrow before returning to China, with the instruction to bin the SIM on arrival. After she arrived, I performed such a swap to a spare SIM I had, using the code that arrived by email.
Of course, this requires that your email password and your giffgaff account passwords are secure!