giving up on a gcseWatch
will it affect my chances of applying to oxbridge if i wanted to in the future, if my other gcse grades were around 7/8/9s but music was the only low one?
Although universities do not usually care what GCSE grades you have (providing you pass English and Maths to a satisfactory level - usually a 6 for Oxbridge), most candidates will have good results in the GCSEs relating to the degree they want to take. For example, if you wanted to get a degree in Physics, then good GCSE grades in Maths and Physics would be useful (though not strictly compulsory).
However, if you're not planning on pursuing a degree in Music and you have a relatively decent set of other GCSEs, then you should be fine. Take the opportunity to enjoy your Music lessons without the pressure of getting a good grade from them.
tl;dr - you should be fine.