Hello,

You may pursue masters in CS at UK even if you are a Mechanical Engineer UG. It becomes easier if your college has a good student transfer program available or if it strongly has some tie ups with these foreign colleges. You are required to give all the required exams to qualify for admission in the UK colleges such as IELTS, etc. However, some colleges also have a policy that if a student pursues UG CS then only he/she qualifies for PG CS. So please have a look at that too. Other than that, you are able to complete masters in CS at UK accordingly

I hope this helps, All the Best!