If you are classed as Home for tuition fee purposes and you are spending the whole of the academic year studying abroad at a partner institution, then you will pay 15% of your agreed tuition fee for the placement year.
If you decide to study abroad for just one semester (on those courses which permit it) then you continue to pay your normal tuition fee for the year.
International students pay 50% of their fees to the University of Birmingham with no fee to host University if studying abroad for a year.
Your host university will be able to guide you in expected living costs whilst you are abroad, however for a general guide you can check living expenses between different countries using this comparison website.