There are three types of postgraduate qualification:
These are usually one-year taught programmes which either lead to a professional qualification or allow graduates acquire skills in other areas. Typical examples are the Graduate Diploma in Education or Graduate Diploma in Computing. There is currently a vast range of courses available in Universities, Institutes of Technology, or private colleges. In the cases of some of the 'conversion' courses in special skill areas, course fees are subsidised.
Masters degrees can be taught or by research. Taught courses typically take one year for full-time study and two years for part-time study. Research degrees can take anything from one year to about five years, depending on how long it takes to complete the research.
A Doctorate or PhD programme usually takes a minimum of three to five years to complete. It may be possible to follow a structured programme for part of the time but in many cases the research is self-driven with supervision from a faculty member.
Some postgraduate courses are clearly more academic than others and require both commitment to research and an excellent academic record. Postgraduate study leading to a PhD usually requires a strong academic background, in most cases a 2.1 degree being the absolute minimum requirement.
Likewise in the case of a Master's Degree by research, a 2.1 degree is a prerequisite. To have any certainty of being accepted into a Taught Masters Degree programme, you need a minimum of a 2.1 degree. However in some exceptional cases a 2.2 might qualify you depending on how popular the course is. Entry requirements for Graduate Diploma courses depend on the level of competition in any one year.
If after four years of study you are still not put off by the prospect of spending another year in full time study or research, then the postgraduate route could certainly be an option for you. You should bear in mind that some taught courses can be very intensive, especially if they are of the conversion type covering completely new study areas such as the Graduate Diploma in Computing or the Masters of Arts in Business Management.
If your interests lead you to a Masters by research or a PhD, be aware that the level of supervision can vary considerably. You should be able to plan your own research and experiments as well as conduct independent literature searches. Ask other postgraduate students about their experiences and talk to your advisor or faculty members before you make any commitments.