Doesnt make sense but apparently its a known issue in the US
Anyway, I called Lexus Breakers in Accrington and spoke to Scott who took the part number and said give him 30 mins, he'll see if he has any.
Good news is - he's found the same unit 86804-53P41. Its tested and working with 2 months warranty and has the SD card inside. £375+vat so £450 all in. Will get my local auto electrician to fit the unit next week and hopefully should have a working radio!