Vısa problem

I am Brıtısh wıth a UK passport and lıve ın Turkey and the law has been changed out here and I can no longer get a vısa from the Embassy ın Turkey. My travel agent ın Uk says he can get one for me but I do not have a UK address .Can I use my sısters UK address or ıs ıt OK to put my Turkısh address on the vısa form and apply ın UK.