GF has just purchased a copper bathtub (used, about 6 years old,
recently removed, no taps). She's been after one for a while, this was
rather cheaper than the 2-4 grand for a new one and quicker than
waiting for me to get rolling one out of sheet.

Any advice on installation? In particular I'm going to need to build
some sort of "tap pillar" to go alongside it.

At present it's copper inside and out. It's going to need a re-polish
before it goes in, but I'm wondering about lacquering and possibly
even tin or nickel plating the inside.