I'm in the fourth (final) year of a single honours mathematical physics Msci in the UK - about half maths, half physics. Obviously it'll depend on the syllabus at where you are, or where you apply to. I can only tell you about mine as an example (my uni is a large top10 ranked one) - I haven't done any experimental work at all, and there are parts of physics I've been able to choose not to learn much about - solid state for example - but I've been able to do lots of relativity, and relativity based subjects, and a lot of QM and QFT from a fairly mathematical approach. There has been some, but not always much flexibility in the modules I've been able to take - obviously you need both core maths and physics, particular in early years.
Maybe think about where you want your career in physics to be, and just look carefully at the syllabuses is all I can say. PM if you want any more details.