Ok so essentially, even if I could source a used MIB2 unit, I'm still going to be up for replacing the amp with one thats MIB2 compatible to get the system up and running? If so then yep it looks like this is going to end up being quite expensive!
I'm not that concerned with Android Auto for this car. It's never had it so I was hoping that replacing the unit with an MIB2 unit would just give me all of the functions the car already had prior to it failing. If somehow it got Android Auto without making any other system changes (apart from a new USB connector) then that would be a bonus.
I've been struggling to find any MIB1 units around, they've mainly only been MIB2 or 2.5. I'll keep looking but I haven't got much hope. The alternative would be to go down the aftermarket route I suppose.
Thanks for your response, much appreciated!