How should I select the correct path for doing my higher studies
For physics PhDs in the UK, the minimum requirement is a 2:1 in your undergraduate degree, which you have (I say physics specifically because that is what I have experience with). However, applications are so competitive that you usually need above the bare minimum to be considered. This means either having a better grade in your undergrad or doing a Master's degree.

My suggestion to you is apply to both MScs and PhDs simultaneously. Then, if you get accepted to a PhD, great; if not, then do the MSc and apply for PhDs once you've done that. Good luck!