Chris Green wrote:
I'm after a very slim 17mm spanner. That's slim jaws, my standard
thickness spanners are 6.5mm thick, I need something about 4.5mm thick
to get into a narrow gap.

Can anyone suggest a brand/type that would be this thin and where I
might be able to get one?

Williams Superslim used to be the must have brand of spanner. No idea if
they are still available.