You say you had Neutral disconnected at the CU but Live & Earth strapped at the CU?
If so forget the neutral paths first of all and make sure you weren't just reading back through another light that was still turned on that you thought was off....
i.e.
1/ When you were at a fitting with the "weird reading" did you take the lamp out as well to ensure no path via neutral?
2/ Are you 100% sure when you did your test that EVERY other light switch on the circuit was also OFF?
3/ have a gander at my quick sketch...
If testing at first light (turned off) and you can still see a path back through for R1+R2 via switches 2 or 4...
View attachment 7832
(sorry its twisted... turn your neck to the right hand shoulder!)
Guinness
the resistance would vary depending upon how many other lamps were still switched ON...
OR..
have you got an extractor fan in circuit that wasn't isolated?
Or TV amp...
Or Smoke detector...
Or anything similar??
opcorn