giving 0701 a go now. Disconnected my disks first - maybe overcautious but thanks Solarfall (I think ).

first flash to BIOS 1 gave same result as EF - wouldn't save settings or AUTO. Flashed again and ok for saves etc.

2hrs ok in 86+ at 450/900 with VDIMM at 1.62V and my other settings for 0403 / 0501. So not worse for me at low clocks/VDIMM anyway.

going to image another system disk and try something more.