I ran it with the polystyrene box and boot floor removed and there’s very little difference. I need to remove it fully and see how much difference that makes, the plastic box will be of very little help to low bass frequencies. I need a second person to help as once your bum comes off the seat it turns the car off.
My son is house sitting so I may have another go when I get home. I think realistically I’m going to have to add a sub of my own either in the boot or under a seat, probably not permitted by Motability though!
Please excuse spelling/typos. Apart from being a clot it turns out I had one on my cerebellum that's now causing various problems!