I've formatted the SD card but the card is not locked (no permission to write) so I can't put the BIN file on it to begin the firmware upgrade. Anyone ever encountered this?

are you using the standard SD that went together with inspire ?  If not try the original SD card

Try formatting the card with using the Go App, before today the inspire always recognised a card that had been formatted using my computer but the only way i can get it to be recognised is to put it in the gimbal and format it using the app.

Then put it in the computer and add the firmware files