I'll w3ade into this subject, as I have, numerous times in the past...
Here in Canada, a rather young, and underdeveloped place, compared with Great Britain; we can easily, and inexpensively wander into the local Chemist shop, supermarket, or even some hardware stores, and pick up a LARGE jug of properly DISTILLED water, at a reasonable price...
So; how come it is such a big deal, to even find the stuff, in the seat of democracy, civilization, and brotherly love ?
I'm not into live steam locomotives, but I always provide a large jug of it if a live steamer drops by for a visit/run. In fact I have two large jugs of it on the shelf at this moment, waiting on a visitor. I think each jug holds 5 litres, (Or more) and the price tag shows $2.50; and that's in Canadian funds...
Fr.Fred