central locking?

my ford focus 03/my central locking is not working had new battery for my key fitted,it is clicking wen using key but doors wont open.took it to fords they think ii could be a relay.but want 75 pounds to do dianostic test first,needs mot soon,is ther any way to get back doors open as i will not pass,or there anything i can do myslf.can any one help me please as money is tight.thanks