As Daniel pointed out you'll need some decent (i.e. paid for) advice on this. If you simply take the stated residency tests it's not rocket science to see that you'll end up resident in both countries at the same time. There are treaties, but my guess is that each country won't want to give up the revenue. If you don't want to pay for advice then I'd suggest googling for the text of the double taxation treaty between Switzerland and the UK and reading it yourself, as well as speaking directly with both tax authorities to ask for their position.