Some people get a Battlefleet Gothic fleet as a side project to compliment their 40k army. I get a 40k army as a side project to go with my Battlefleet Gothic fleet.
Unfortunately my vast armada of glorious Kor'vattra ships is far too dear to me to send them away, but if anyone else is less attached to their Battlefleet Gothic ships then please discuss details with Yourand
via PM, in accordance with ATT policy on trade and commerce discussions.
In the meantime Yourand, might I suggest you include a short reminder as part of your signiature? Something like a quick 'Battlefleet Gothic Tau wanted - PM for further details' or similar can help a great deal if the models you're after prove elusive.