All employed staff are entitled to paid holidays so that is not going to tell you much. And all staff earning over a very low limit (that would only really apply to very very part time staff) are entitled to statuatory sick pay.
I would suggest that a more appropriate and revealing question would be how long the staff have been there for. If it is a small nursery, you could find this out about ech memebr of staff. If it is a large nursery, perhpas just ask about the staff in the room your child will be in. If they have high staff turnover, it is not a good sign. Althgouh turnover is high throughout the industry as a whole, a good nursery will be able to hold onto its key staff (particularly those in senior management) for a long time. All nurseries will have some turnover - and this is a good thing. However, it really should be limitied to just a few staff replaces others who have moved on for reasons such as starting a family, personal circumstances etc. Of they may have new staff due to an increase in the numbers of children attending. If on the otherhand, lots of staff are leaving to go to other nursery jobs, its a problem.