Bit of a downer for the UK to see them list in the US, I do understand they just want access to the most capital, but I find a shame LSE is not competitive for this kind of thing.
What about indexes? If they qualify for NASDAQ or some other major index, there's some "mandatory" investment that gets triggered by a bunch of funds that do index tracking.
I would presume where you choose to list is kind of a flag of convenience, like it is in maritime. It's probably not as irrelevant as to where things actually happen as flying the Liberian flag or incorporating in Delaware but I'd bet it's close.