UK degrees can take only three years and postgraduate Master's courses only one year - compared with four years and two years in most other countries. This means you will save a great deal on both tuition fees and living costs - and you will be able to start working and earning money sooner. UK degree courses are shorter because they are more intensive, and therefore more efficient in terms of your time and money.
Admission is based on individual institutions' requirements, since there are no pre-requisite tests (other than for English proficiency).
Most universities require good performance at the undergraduate level, in relevant area, in order to consider admission into their Master's level programs. Most Master's programs are of 12 months duration.
MBA admission requires work experience of at least 2-3 years at the managerial level, in all decent UK universities.
And, unlike in the US, PhD applicants need a Master's degree. Otherwise, applicants could register for a M.Phil. degree and transfer to PhD program if the progress is good.