Thanks, You are right -The continuity readings should be similar. If they are both correct (which they quite probably aren't) then the high one appears too high, because for 6mm² T&E cable R1 +R2 should be around 0.01Ω/m. 0.88Ω implies the cable is over 80 metres long which surely isn't correct. 0.15Ω looks entirely plausible, therefore the excess of 0.63Ω could indicate a high-resistance joint in the neutral that will heat dangerously under load (at 20A that's 252W, the heat of ten soldering irons)
The insulation resistance L-E at the fault seems to fall in the middle of the two ranges on the tester, off the bottom of the scale for IR (reading 0.01MΩ or lower (you can't tell how low when the display is showing the lowest possible number other than zero) but off the top of the scale for the continuity test. This is a limitation of most MFTs but we don't really need to know the actual resistance as it's definitely no good as it stands.
So what we can infer from the readings if they are all correct is that the insulation of the line is seriously low, possibly low enough to overheat dangerously, while the continuity of the neutral is seriously high, possibly high enough to overheat dangerously. The readings don't enable the location of the damage to be narrowed down.
New readings for Continuity:
LE 0.11 ohms
NE 0.12 ohms
(Dodgy crocodile clips I think: will use WAGO connector in future).
IR results are the same.