Do British expats also pay taxes back home?
It depends: there is an international agreement between particular countries where things are set up to avoid people paying double taxation, the paying of similar taxes twice - in the place of "residence" as well as in their homeland, Britain, in this case.
There is also a set of agreements that allows wills to be drawn up to suit the native land of origin. Unfortunately, it doesn't seem to apply to the act of
inheritance, so regardless of whom your money is going to, the Spanish, reasonably, want their pound of flesh from anything you hold in Spain, which is a good reason for not dying here if you have children you love. :-)
A bone of contention is the difference between residence and domicile. Not as simple or clear as that might look at first glance.
Worse, for the really rich, you can't just buy a superyacht and live on that, and escape all taxation, either. My heart truly bleeds!
:-)