I have never read on this site a 250K+ wage outside of US.

It's wrong because of existence disproof. Right now, there are lots of people writing software outside of the USA and billing more than $300k to do so.

And the answer to your second question is "anywhere with power and internet." That is the subset of places from which one can telecommute to the USA, where there exist dozens of large software companies that hire remote staff. For that much money. Honest, no foolin'.

It's sad that I find myself repeating this here so often. Nobody seems to want to believe that their industry pays as much as it does.

Places like Dubai and Middle East could possibly land that sort of salary. In the UK, it's highly unlikely, only if you work for a giant corp and are seriously valuable to them could you get close to that figure. You'll probably end up having to step into a CTO type role though.