Peugeot 306 estate?

Hello all, I have a 2000 V reg peugeot estate 306 - and I have a car seat called Nania - it was purchased from Argos and is a multiway car seat - although I have the instructions for it to be fitted it doesnt want to go in my car for some reason - I cant really afford to go out and spend more money on another car seat - any ideas please?