It's perfectly normal for salaries to depend on location, even within one country, and even within quite a small country like the UK. So the problem here is the

It's perfectly normal for salaries to depend on location, even within one country, and even within quite a small country like the UK. So the problem here is the "level", the seniority/role/title/whatever, not the salary. In general I do rather have the impression that the best way to have a "career" is to change employer every few years. I'd say, go for it.