asda returns policy help really peed off

Hi i'll keep it short I bought guitar heros world tour band version from asda on the 23 of jan the cymbal on the drum kit stopped working on the 8th of march packed it all up went to asda tonight to return it with my receipt only wanting an exchange which has never been an issue in the past with any thing faulty was told i would have to contact the manufacturer and return it to them as they changed their policy at the end of jan.. but i bought mine jan 23 and was not informed of the change of returns policy when purchased this applies to ps3 wii and xbox consoles and games so i'm told i've now come home and checked out The Sale of Goods Act 1979 just want to know if i go back in tomorrow armed with necessary print outs and start going for it that i'm in the right. after all i don't want a refund just an exchange
It is the seller, not the manufacturer, who is responsible if goods do not conform to contract

If goods do not conform to contract at the time of sale, purchasers can request their money back "within a reasonable time". (This is not defined and will depend on circumstances)

any help and opinions or ideas would be helpful as i was spitting teeth when i came away tonight:mad: :mad: :mad: