Same question also applies to professional indemnity insurance renewal forms. Not easy to answer this question as yes we do in some circumstances, but no in other situations.
We do get locums willing to be named as cover for the purposes of PII renewals and lender panels, but it tends to be where they have a relationship with firms already, and the name to lender panels is part of the arrangement. In other words, if a locum is providing ongoing annual leave cover, knows the practice and the lawyers in question, and is aware that there will be work arising from the arrangement on an ongoing basis, they are usually relaxed about their name being used.
Other than this, locums tend to want a monthly retainer in order to be the named cover, which can be expensive just for what is a box-ticking exercise. At the time of writing we would imagine £200 a month may attract some interest.
In the past some SRA regulated firms have got round this simply by asking a specialist locum solicitor recruitment agency like ourselves to confirm that we could provide cover with at least 24 hours notice should there be an emergency, but we have not been asked to do this for some time and it may be firms are now being asked for specific names of lawyers.