Planning permission for cellar

[StarTravels]

We are thinking of buying a property which has an external barn which has been converted into an office.

It was converted back in the early 90s and I've got a copy of the planning permission and it all looks fine except that on the plans it doesn't show internal stairs within the office the lead down into an underground room.

They are describing this room as a wine cellar but it looks quite unlike a wine cellar to me. There's a metal safe built into the wall, and the whole room is made of concrete and metal. It looks more like a bomb shelter or similar!

I was surprised there's no mention of the stairs or the room on the planning permission and I'm worried if this is going to be a problem for us buying the property. I'd also want to make sure it was safe. The underground room is pretty large. Around 30' x 30' and I'd take a guess that it's around 10 feet high, so it's quite deep.

Is this something I should be worrying about and is there any way I can make sure it's safe? Can you find out if a structure was built with building regs etc?