I am an undergraduate who is interested in doing a PhD in the UK in the future. I am aware that there is funding for living costs, tuition fees and travel costs. But if a PhD student is self-funded, do they fund their own research too? Or will the university pay for the research cost?
Although the exact answer depends on the Department, in general, self-funded students do not have automatic support from University or Department in relation to their research expenses. In the UK, PhD studies are considered training and hence a service to the student. PhD is not a job, but a period of learning. The contributions that students make to the Departmental research are not usually appreciated or properly considered in policy-level discussions. As a consequence, self-funded students often are not supported at University level. They may be supported by their Department or supervisor, on an individual level, rather than systematically.
Depending on the field, the supervisor might be able and interested to cover some of the research expenses incurred by the student. For example, if a PhD topic heavily rely on computations, access to HPC would be required. Some Universities charge academic staff for access to their computing resources (after charging overheads to grants won by academic staff). The student could struggle to pay these fees due to admin and financial constraints. A simple solution would be for supervisor to cover these costs from their own grant or computational budget.
Other expenses, like conference attendance, are also considerable, but often not something a supervisor would cover.