I understand. I know he checked the whole lot, as we needed a new unit in the house. If I start replacing it and find problems, I'll get someone in to do it.Double check that @Westctony .
Having a loft conversion done, the electrician then would have just tested new or modified circuits, unless you specifically asked them to do the garage too.
Please don’t think we’re trying to put you off. The comments raised have been valid about grouping factors etc.
We get a lot of complete numptees on here asking for advice, and we wouldn’t forgive ourselves if we told them exactly what to do and they ended up burning their house down.