There's no legal reason why you should not combine different schools.
However, just as it's wise to stick with one instructor for the best part of your training, it's also best to stick with one school. Just think about the hoops the instructors have to jump through to keep each other updated on your progress. Within one school they typically have a single cabinet where all student files are kept, so if you go from one instructor to the next they can simply access your file and be up to date. With two schools this is going to be virtually impossible. And your learning may suffer.
And then I haven't even started on the legal documents that the school has to keep on your behalf. Including the results of your ground exams, the QXC paperwork and so on.
My advice would be to stick with one school, but simply visit the other place on your x-countries. Once you've got the license you can always become a member of both clubs (or rent at both schools) if you want to.