If the manager and new member of staff were both not vetted, then I consider it to be unacceptable.
England - Full Day Care National Standards
Standard 1
1.3 The registered person ensures that any person who has not been vetted is never left alone with children.
1.4 the manager has at least 2 years experience of working in a day care setting;
Are you sure that the manager has not been vetted?
I would consider it unusual for a nursery manager to be working, if their checks had not been completed. They may have had a check done in their previous job, and thus are in the process of having that check updated due to changing job. The nursery owner may have been satisfied that the previous check was sufficient to allow the manager to work, while they await the updated check.
Talk with the nursery manager to establish exactly what the situation is and to make them aware that you are not happy about it. If you do not get any joy from that, then contact the nursery owner (registered person) - this may be a company name, or an individual. It is shown on the Nursery Inspection Report. Think it is also shown on the printed Registration Certificate, but it isn't shown at Ofsted website version of the certificate.
Nurseries are often unsettled when a new manager arrives. It can however be good, as the new manager may reallocate staff and resources to better meet the children's needs, plus be more approachable, so parents can chat with them better.