Cracked it. Downloaded another copy of JJ, installed it but same scenario. Installed SS5 but managed (with some difficulty) to open drop down menu on the home page and install the usb storage. I'm wondering now whether it was there on JJ but for some reason couldn't open drop down menu. My fingers are not the best for these phones. Thanks all for your efforts.
PS First reaction to SS5 is that it seems better than JJ so some good has possibly come out of this.