So it looks like new rear much time but shimano seem to have rewritten the book on this one
My current lx much drops to the small (high) gear with no cable on …high/top normal, now it sounds like Slx mech is low normal using above logic will move to big ring on cassette (low gear) but after some discussion in shop low is now the small rear gear have I got it completely wrong often happens or do I need to find different mech thanks confused

SLX mechs are all top normal. They all sit at the smallest sprocket when there is no cable tension i.e. they are in top gear.

thanks mrP sounds more hopeful