Now I am left with where and how to mount it.
This is my first choice, though i'm not sure it will be easy due to there only being solid metal on the bottom half of it

here would be easy to reach and install but my leg hits it whilst on the foot rest (not too big a problem though)

and here it may restrict seat forward movement, but would be out of my way the rest of the time

any other location suggestions/feedback?
also are there any requirements as to how it is mounted? ie what sort of bolts/screw are used? and what it can/cannot be secured to? where have other SW20 owners with a fire extinguisher mounted theirs?