Hey, I also hold a UK bachelor degree and I don't know how to convert the grades into GPA. I have asked several universities and they said they won't convert them at all since their faculty are familiar with the UK grading system.
I obtained Mathematics bachelor degree with a second upper class in a Top 4 UK university and an MPhil in Social Science degree with a GPA of 3.8. I am not sure whether my GPA reaches the threshold for applying top PhD in Political Science programs in United States.
Many thanks in advance!