If you are a full time student, you will pay full time fees for three years. If you have not submitted your thesis by the end of this period, then you may pay for an optional one year writing up period.
If you are a part time student, you will pay part time fees for four years. If you have not submitted your thesis by the end of this period, then you may pay for an optional 'writing up' period of up to two years.
You are responsible for meeting all of the costs related to your own research project, beyond the resources available in the department.