how to bypass a renault megane 1.4rn paris p reg?

hi i have a megane 1.4rn paris which i lost all my keys for i got a new key from renault and they can not program it to the car they said it has had a system change in its lift time and the only way is for a new system to work which would cost over £800 can any one help as renault dealers are crap and just want your money and lots of it and not very helpfull