Rain water harvesting as sole supply to house

I have seen it done in one place. I don't think their setup was very good as they used an old kerosene tank and they had no treatment system.

You will need to treat all your drinking and showering water to kill the bacteria. You can use UV filters or reverse osmosis ones for that, they can be a bit costly to run as the RO system requires new membranes now and then. For the jacks, garden hose, washing machine you can get away with untreated. You will need a couple of IBC tanks. There are underground tanks you can get as well but they are mad expensive. Cheapest is IBC's and maybe build some wooden frame around them so it's not so ugly. Have them all at exactly the same level and join together.

You have prob explored all these options in the past anyway but just to let you know there are small drilling rigs out there too which arent much bigger than a car trailer, had one for doing the bore holes for GSHP system. Must be an incredibly difficult site?

It was a subcontractor of the heating system supplier (REC renewables Killarney) they my be worth a ring, but it was something like that