Hi, I also have an offer to study politics (/economics) at Glasgow. When I went on the offer holder day they explained IR will have different modules in years 3/4 which focuses more on the relations between different countries/states. However for anyone studying politics you can still take IR modules in 3rd and 4th year as part of the politics course but priority is given to those studying IR. They also said to study IR past 1st/2nd year you must have applied on UCAS (so if you want to change it you should probably contact them) rather than changing at the uni due to high demand. Politics however you can switch to take it at honours.