PS, to answer a few old queries from higher up:

As far as I can tell it is still adults only.
Sparkling wine is available at breakfast. (You haven't lived until you've had a breakfast including sparkling wine flavoured with coconut).
Massages are 1750 to 1950 SCR (100 - 110 GBP) (15% discount for Diamond)

Also, as noted by previous commenters, the Northolme seems very resistant to granting a late checkout.
I know there are several international flights with early arrivals and late departures, but the resort is nowhere near capacity and they issued a flat refusal without even checking.