Where to sell a leaseback?

I have a 38 square metre top floor apartment in Paris, St Denis with a double width balcony and underground parking space. The rent is paid regular at 1930 euros a quarter and has been for over 2 years, a Metro station will be opened with 1000 metres by 2012.

I want to sell, can anyone point me where to go and who to use, what I might expect to sell for? Will selling with the lease intact cause problems, restrict buyers?