So I had one child at Mouse House and one at Noah's Ark so I can't answer your question directly, but having experienced nurseries with both kids from a young age, I would go for a morning session. Kids are less tired and more open to new experiences in the morning - especially if this is the first time they are going to nursery, you will find they will settle much easier with a morning session, and they can get home and have a nap after. You might find they are more likely to nap for the first few weeks after starting nursery - it's such an overwhelming experience for them, they get shattered. For example, my daughter had dropped her nap by the time she started at a nursery school, but ended up returning to napping at lunch time (often in the buggy on the way back) in the first couple of months.
Mouse House is a great nursery, I am sure comparable to Marmalade Cat. So is Noah's Ark and much cheaper than Mouse House - the only reason we went with Mouse House for number 2 is because it's a lot closer to us, which makes a big difference once you have two kids to go to two different places. I can't say I personally loved MH staff and management - their attitude was often "taken it or leave it", and I felt they weren't very "customer-focused" in their approach. However, the staff who worked there were amazing, and my child adored it and had a great time. I think staff turnover can be quite random - it could be a couple of people leaving for personal reasons in close succession, plus, it is quite demanding work!
Best of luck,