Hello,

The eligibility criteria for MSc Management in UK is passed first or upper second class Hons degree from a recognized university securing a minimum of 60-70% aggregate,

candidates are also required to pass English language proficiency test which is to be submitted along with the application form such as TOEFL/IELTS,

many universities also require GMAT/GRE scores for admission though it's not manadatory for all but having one is a greater advantage,

in regards to your specific query about coming from arts background to pursue MSc Management,  Imperial College Business School offers MSc Management to candidates beloning to non-business/management background as well,check out at https://www.imperial.ac.uk/business-school/programmes/msc-management/admissions/entry-requirements/#-academic-requirement-----undergraduate-degree-at-2-1-honours--or-international-equivalent- to know more details regarding this,