How can i find out the ground rent and service charge for an apartment i want to buy?

It's a repossession, and the estate agent can't find it out. I've asked the mortgagee in possession and they don't know, and i've spoken to the current residents in another apartment in the block and they don't know! Is there any other way to find it out? Thanks:-) UK|||Well somebody must know ,how else is the ground rent going to collected. The other residents must be paying something to someone. The Estate Agent needs to find this out not you.