Bit more of an update. The sinking pedal seems to have gone. Between the previous efforts to expel air from the ABS unit I replaced the rear flexible hose (the fronts were done a few months ago).
I now have a pedal I can trust - even if it does feel a bit spongy still. Maybe the old flexible was part of the problem, maybe another bout of bleeding made the difference. Whatever it was I now have a pedal I'm no longer petrified of just disappearing to the floor - which is where I was when I started this thread.
If there's anything else I do that brings improvements I'll post further but meantimes, thanks to all who contributed. Your help is greatly appreciated.
I now have a pedal I can trust - even if it does feel a bit spongy still. Maybe the old flexible was part of the problem, maybe another bout of bleeding made the difference. Whatever it was I now have a pedal I'm no longer petrified of just disappearing to the floor - which is where I was when I started this thread.
If there's anything else I do that brings improvements I'll post further but meantimes, thanks to all who contributed. Your help is greatly appreciated.