Last saw him with the Argent spin-off Phoenix years back... rip...
Vaguely remember a modular P/Strat he used...?
Yes! As a Strat/P it looked like this:
And as a P bass:
Rod Argent's Strat was also much modified, with the top horn shrunk down and a lot of holes added:
I'm not sure if this was done by the band themselves or whether an early luthier like Dick Knight or Sam Lee did the work. It doesn't look like John Birch's handiwork.
It looks like Jim also had a Mustang (going back to the '80s or so?) with PJ pickups fitted. He brought this out recently, as well as Status headless basses. The Mustang is here:
And previously:
Anyway, RIP Jim. Falling down the stairs seems an unfortunate and tragic way to go, and one which could potentially claim any of us at any time. Very unlucky.