Well first a big thank you to all who replied to my original post.
Gutsibits were great but could not supply a replacement micro switch (at any price - they had one listed for £50 odd quid which I would gladly have paid) and sold me the hydraulic solution.
Thing is I am adverse to “escalation” repairs as it tends to open cans of worms (dissemble brake system, add switch, break something in process, need another gasket - unavailable etc). So I thought I’d persevere on finding a replacement switch. And vioila!!!
Under a fiver.
Now the thread is (I think) a fine metric which is no good, but as brass was easily re-cut to M6 with my tap and die set (hasn’t been used for years but just paid for itself). Works perfectly and looks a better quality as well. Got a couple spare so that particular problem is solved.
I believe there are a few models where this might help.