>but where the new headquarters sits isnt a big deal.
No, it *is* quite important.
Apart from anything else, they currently pax their taxes here. But it's become more common over the last 5 or 10 years that UK companies have been taken over and notionally restructured so they're a production facility of their non-UK owners. Profits got back to the parent company, and the country (effectively *us*) lose a lot of tax revenue as a result, despite the fact that that the UK company, as was, may not have changed in essence.
One link here (first hit on google), but the issues's been in the press a few times over the last year (including yesterday's Guardian, I think)
http://www.thisislondon.co.uk/markets/article-23796668-city-talent-isnt-as-vital-as-cadbury.do