Thanks Nigel - yes the bracketry within the boot - I'll try to attach a couple of photos but I'm struggling with a dying MacBookPro at the moment so I'm juggling stuff.
Mark, yes, it's the two brackets in the boot. One underneath the left side light and the other towards the centre. Photos will help but the measurement is what I need.
And yes Nigel, the four square brackets underneath the car were for build purposes but on my car, when the sills were opened for repairs Geoff T built in strengthening structures to allow me to use these as jacking points! Inner and outer sills and floorpan are all tied together there now.