Hi Harry,
We have the same here in Denmark Hill Estate too. It is unbelievably high, they estimated £3,368.77.
We are so frustrated. I am not sure we will be able to renew our mortgage as the banks don't want to take any risk on high service charged places.
I need advice from the Leaseholders' Associations as we don't have one here and I would like to register it asap to question bills.
Have you taken any actions already?