Here at Nottingham we are running an MSc in Gravity, Particles and Fields. This is very specifically aimed at students interested in getting into relativity and particle physics research, in areas such as quantum gravity, cosmology, quantum information, etc.
The MSc runs from each September and applications can be made online at any time. More info
Update There are some grants for well-qualified students, the details depending which country you are from (or currently in). Details are under the funding tab.