Could they be programmed in a UK layout and how much would it cost?
They certainly could be programed as uk layout boards, they could even be set up to fake ANSI and output in ISO uk layout by changing the output tables in firmware. (soarers converter) but if they were just setup in regular ISO and the keyboard layout was changed in your computer settings, that would work as well.
The only real difference I see would be that a few keycaps would not match, and so you would have to get a replacement keycap or two.
I was unable to find complete UK layout keycap sets from Unicomp, but perhaps they just don't have them on their site.
As far as cost, I don't charge extra to customize the layout since I always have the boards open anyway when I do the rivet replacements, so it wouldn't be a problem to swap a hammer or two and turn it into an ISO board.
My boards generally sell for one of 2 prices: $125 for class B restorations: might have a small scratch somewhere on the case, or maybe some of the keys are a little shined from use,
and $150 for Class A: essentially brand new, a perfect board that could easily pass as new in box.
All my boards have full rivet replacements done, and have an internal Soarers converter, with a flush-mount USB/B connector, and include a Premium Nylon Braided USB Cable.
I am currently working out a way to provide full warranty support for my conversions, and all of my boards will be grandfathered into that warranty. (More on that later on)
-Ezra