Thanks everyone, sorry I posted this and promptly went on holiday - AFK! Looks like the discussions went off at a tangent which is always good on forums :)
@MWJB is right it is the SCA recipe from here https://www.baristahustle.com/blog/diy-water-recipes-redux/
@MediumRoastSteam thanks for the suggestion on .1g per 1L. I have the bicarbonate of soda already. That seems very high (everything is relative of course!) though compared to 0.04g as per the SCA, is that because it can take more alkalinity if it doesn’t have any hardness in it?
I will get an order in with some of the recommended suppliers for Mg.
@Rob1 I will try to track down where I heard the pseudoscience :)
As to buying a second hand Minima, although it is temping I don’t know if that would sit right with me. I know what I’m like and there would always be the feeling that, because I didn’t have it from new, anything that went wrong might be because it was second hand. I own other second hand things (my motorbike for instance) but something about the potential scaling issues makes me nervous. Maybe if I could guarantee that the previous owner only used pristine water from the holy river Ganges or something (😉joke, I know that would be a terrible idea).
As to importing a machine, from a thread that, again, I saw on some forum that I can’t remember - the Minima ended up costing somebody an extremely significant import tax what with VAT etc, from what I remember it ended up not much short of a new Bianca but again that could be hazy memory.
Thanks again everyone
Ollie