My central locking wont work atal in my mk5 golf. I've ?

My central locking wont work atal in my mk5 golf. I've tried my spare key and replaced the battries, but still no luck.i took it to the vw dealer and they said its the convience box or a loose wire...any way of finding out without spending nearly £300 (thats the box and labour) in the mouth of xmass??

thanx.