Has anyone converted their cellar to living quarters?

[dancingphoenix]

Can someone guide me on the cost of converting my cellar into living space? I have a ground floor flat in a victorian conversion in London. Lucky for me it came with a dry cellar which i am told would make a nice living space. Some of the height of the cellar is 6ft + whilst in other places its just below 6ft. Its 30ftx16ft and i can see daylight through the old coal shutes to the front of the property. I can also see into the back garden through a gap in the wall which appeared to have been bricked up.

I have been given some absurd quotes ranging from 2k to 35k but after research on the web found i can get the job done for around 10k to 15k. Can someone provide me with a guiding price?

Also i think i need to underpin the property and am told this is quite expensive. Again, has anyone had to underpin their property and want to share with me their experience and cost.
Thank you for your help.