as an ex car dealer if it's a straight finance lease (no ownership) then you will most likely have to pay all the remaining payments (although read the contract as it may allow you out of you have paid more than x payments (it will be in very small writing!!)
If it's balanced payments then you should be able to get out immediately (but unlikely at 100/mth)
If it's Lease Puchase/HP then you can sell the car and hopefully clear the debt with little or no settlement…. From memory i think select 3 is HP, but cant be sure!!
Good luck
P.S. if you cant get out you can always have a deal on the side with a mate and rent it out, but make sure you get it fully insured (and dont tell the lease company!!)