Sold a dodgy car of ebay gave them my car and cash?

if the car is as described by you then it should not have passed its mot ..i own an mot station ..this is quite serious if true ..tell the dealer you are going to contact VOSA .that is the governing body for mot s..the garage responsible could lose their licence to do mots ..if no joy then do contact VOSA .they will examine your car ..and decide if there is an issue ..but you were very silly to hand over your car and V5 without driving the other car first ...and your tigra was worth more than the 206 in the first place ..all so try trading standards