TBM, I did that core plug recently on my old '74 4/4 before selling it to a friend. In the end although car was low mileage did all the core plugs and replaced all gaskets on the engine; I do work slowly so it'a a lot of hours and my previous post is maybe affected by incredibly high labour costs here in France. I forget that there are indies in the UK who are extremely reasonable, and your core plug replacement sounds like one of those jobs.
Cheers
