I wouldn't discount the issue of intellectual capital. There are just a handful of universities in the UK that produce world class level work in CS. While there

I wouldn't discount the issue of intellectual capital. There are just a handful of universities in the UK that produce world class level work in CS. While there are dozens of such universities in the US. Numbers like that make a big difference. And if I remember correctly, PhDs in the UK are kind of weird compared to the US. Your thesis has to be research that you haven't published yet.