Just wanted to do as I didn't have one.

I would differ from uni to uni and from candidate to candidate. I didn't have one either but some people at my uni did...

Varies a lot and depends on whether you are already known to your potential supervisor. I didn't have an interview.

Thanks for the replies. I know my supervisor from being a student of hers a lifetime ago so I guess it would have been superfluous. I'm grateful for it though as I'm not at my best at interviews!

Depends on the subject: I'm sure most science ones have compulsory interviews unless you are going straight through from an undergrad or Masters level lab project.

Humanities, no idea... but I am under the impression the whole process is different from sciences.