hi mitsypie, I think you are actually asking about what qualification comes after your undergraduate degree? If you know that you want to proceed with a PhD, then your quickest route to this is via an MRes (Masters in Research) rather than an MSc (Master of Science). The reason for this is that most MSc's are 1 year long, followed by a PhD of approximately 4 years. With an MRes, you do this for 1 year, but it leads directly onto a PhD which is usually then completed in 3 years.
Good luck with your studies!