Where/how are you doing the IR test? !

is there a logical reason why the N-P reading was so much lower?

(hello...... Neutral and earth are closely connected, don't you know)
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local