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Bulkier than mine but I think it might fit in the mk4 centre arm rest box ,and certainly in the under floor compartment.
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I'd like to repeat a clever thought by ninanina: If you put it the jump starter into the under floor compartment in the boot and the 12V battery is
really flat, you wouldn't be able to get to it (easily!) as central locking wouldn't work either!
So, you would have to go through the rather awkward emergency unlock procedure of the hatch and/or do some contortionistic wriggling to get to the under floor compartment from the inside of the car.
I admit: I'm (still) keeping mine in the under floor compartment because I haven't figured out (yet) a clever way to fix it in the footwell under the driver's seat (which - I've been told - is the least favourite place of back-seat passengers).