I've finally installed a fire extinguisher in the cab, much better than having one in the boot I think:
I went with a 2l Ajax/ Chubb foam extinguisher mounted under the passenger seat (LHD car) on a bracket made from 40x40x200 aluminium angle pop riveted to the seat frame. I've tested grabbing it from both seats and found no issues. I'll do the same for the 900 and I also installed two new 6l foam extinguishers in the workshop whilst I was at it. I hope I never need any of them.