From EYFS Statutory Framework (May 2008 edition)
"there should be a separate baby room for children under the age of two, but they should be able to have contact with older children and be transferred to the older age-group after the age of 18 months or as appropriate for their individual stage of development."
Does not sound as though they comply with that... could you e-mail me their URN (or Name + Postcode) so I can take a look at their inspection reports - may help show how they do manage a 0-3 group room. See my profile for contact details.
When I've worked in nurseries... small nurseries have often only had 2 rooms - one for under 2's and one for 2-5's. It actually worked very well but the number of children being cared for was low. The Under 2's room for example was limited to 6 children.
Is this a very small nursery... say registered for 24 children in total? If so then the baby room may well have a 6 child limit and children aged 2+ may well be mixed in with the older children most of the time.
While the nursery may be registered for children from birth... they may not actually take them from that age. Ask them what age children they currently have in that room. You may find that one or two are under 1, others are 1+.
Main time of problems was Lunchtime, where it can be all hands on deck with feeding. Fortunately with children of that age, some will feed as and when needed, rather than on the nursery lunch schedule... some one or two may have been asleep by the time the older children sat down for lunch.