1600 gross works out about 285 nett so if you can find a nanny in ipswich who will work 5days for that, then might be worth employing a nanny.
good points, nannies will still look after children if ill, and are generally more flexible if you have to work late/get stuck in traffic etc
bad points - as jura said nannies do like to go out and about, esp in holidays, though some like me do try and limit BIG trips and try to get vouchers,make picnic lunch etc to cut down costs - also petrol costs can be high if you dont previde a car
good points - nurseries, once you have paid out money, you shouldnt get any hidden/extra costs so easier to budget
bad points - if ill, nurseries dont normally take children
a nanny will be paid the same whether one child at school or not, as they are still on call
childcare vouchers are a godsend, nurseries will accept them, and if your nanny is registered(cost to you£100) then you can use them with her as well - which really help with the costs
have you thought about using a cm,as possibly cheaper