With regards to the MCB... It does trip when turned on... But NOT instantly. Takes between 8 and 10 minutes roughly which I find strange.
It is strange,
An MCB trips when there is too much current flowing. A broken wire prevents current flowing. The exception to that is when the broken end shorts to another bare wire but then the current flowing will be high enough the trip the MCB almost immediately.
It might be that as you walk around looking for the fault you stand on a floor board under which is a damaged cable. Your weight squeezes the cable pressing damaged ( bare) conductors together causing a short circuit which trips the MCB. The damage may include a broken Neutral which would explain the voltages you are finding.