I found the problem, it wouldn't install because usb-v2.ko was already installed, but obviously the wrong version
A system restore didn't fix it so I reflashed a backup then deleted the usb drivers in /lib/modules/3.13.5/kernel/drivers/media/usb
Rebooted
installed the DVBSKY plugin, rebooted, and the usb DVB-T330 works perfectly, I now have dvb-c tuners working perfectly in my Duo2 (2 of them dvb-t330's)