Taught courses provide an opportunity to enhance the knowledge in the subject previously studied or to study a new subject. PG courses in the UK are very intensive. They can be completed in an academic year whereas in other parts of the world it takes two years. You may heard that Postgraduate work is a lonely experience. Yes it may be, compared to the camaraderie of an Undergraduate course.
Postgraduate certificate is designed particularly for non standard qualifications.
In addition you also need to prove your English language proficiency. Tuition fees for PG Diploma will be very much lesser than this. Also it varies from Institution to Institution and from course to course. The rural town you choose your cost of living will reduce considerably, which means living in Bradford is cheaper than that in London. It has been roughly calculated as a single student needs 6500 pound sterling's for one year full time study.