How long do retailers have to give you replacement?

Here's the thing. I bought a pair of Beats by Dr Dre headphones at christmas last year and they've recently become very crackly and the ear tips get stuck in my ear so I wanna take them back to the shop I bought them from (hmv) for a store credit rather than a replacement. Do you think they will give me a store credit? I have all the original packaging and receipt. The argument I would use is that obviously the headphones are faulty and the ear tips have been getting stuck in my ear which could cause serious problems. Thank-you.