Caporegime
@norm did you get a torr gauge?
That will be far better for doing a rise test. Vaccing over night is bit extreme assuming your trusting the valves in the system not to let by
I would have liked digital vacuum meter but it's a bit hard to justify the expense for a one off installation. Guides online and YouTube videos seem to have success just using the manifold guage method to monitor no changes.
I wasn't going to run the vacuum pump overnight, only 30 mins, then leave the guage attached to see if it's lost any vacuum the following morning, how reliable this will be I'm not sure as you then the valves could be leaky on the manifold.
I think for complete reassurance it has to be a nitrogen test at 200psi, but that's £134 for a regulator and £40-50 for a bottle of nitrogen? Again hard to justify.
What is the approx size of the outside and inside wall units please? As much as I'd like split AC, I don't think I have room where I'd prefer it to be. Going to also look at alternatives (think there is a air pump or something else which may help a bit but obviously not as good as AC). I gather you can get water cooled AC as well but its more expensive.