A realistic, but non-specific salary bracket e.g. I'm looking for a starting salary somewhere between £20,000 and £25,000.

Speaking about salary can be awkward for some applicants, and during a telephone interview is no exception.

Honesty is the best policy here. Give a broad salary range which you feel is realistic to the role, its responsibilities and your previous experience. Any further negotiations can be brought up later in the interview stage.