2005, 33,000 - purchased 3 weeks ago.

we have just purchased a bmw 535 touring from our local dealer, we took delivery of the car on the 24th April 2007 and within a week the entire incar computer stopped working, and discovered that the roof rails were corroded. My husband booked it into the garage to have this fixed and in the meantime we took the vehicle on a long weekend to France, during our trip the warning light came on to warn that we had a puncture, this was checked by the garage in france and found to be fault (ie we did not have a puncture) - we took the car into the dealer last Wed (16th May 2007) to be told that the car did in fact have a punture and it would cost us £216 plus vat for a new tyre! We were not prepared to pay this price so booked the car into another local garage (which we have used for years and trust) to fit the new tyre - I collected the car from the dealer this afternoon (21st May 2007) and took it to have the tyre replaced, the trustworthy garage discovered that a) dealer had curbed the alloy on repair b) two rear wheel rims cracked and potentially very dangerous, thus indicating to the on board computer that there was a puncture when in fact there was not! I am very upset and would like to reject the vehicle, cancel the credit agreement and have a full refund - how do we stand legally?

we have just purchased a bmw 535 touring from our local dealer, we took delivery of the car on the 24th April 2007 and within a week the entire incar computer stopped working, and discovered that the roof rails were corroded. My husband booked it into the garage to have this fixed and in the meantime we took the vehicle on a long weekend to France, during our trip the warning light came on to warn that we had a puncture, this was checked by the garage in france and found to be fault (ie we did not have a puncture) - we took the car into the dealer last Wed (16th May 2007) to be told that the car did in fact have a punture and it would cost us £216 plus vat for a new tyre! We were not prepared to pay this price so booked the car into another local garage (which we have used for years and trust) to fit the new tyre - I collected the car from the dealer this afternoon (21st May 2007) and took it to have the tyre replaced, the trustworthy garage discovered that a) dealer had curbed the alloy on repair b) two rear wheel rims cracked and potentially very dangerous, thus indicating to the on board computer that there was a puncture when in fact there was not! I am very upset and would like to reject the vehicle, cancel the credit agreement and have a full refund - how do we stand legally?:-?