Thanks and my apologies, made a typo, earth electrode resistance needs to be 2ohms or below , not 20ohms and is TN-C-S.
Arrived with that value with formula ohm max = 230/(60x2) = about 2ohms.
As its a 230vac 60amp installation.
I managed to get a much longer spike down and need to retest, however the plot thickens... my Meter may not be working properly x) MT330, have had ongoing issues and just been calibrated.
I'm going to borrow a friend's Meter and retest.
Andy the only reason I'm not pulling out my hair is that I recently raised my prices so feel quite happy with the profit margin on this job.... but that extra profit is probably now gone lol