Unfortunately Games Workshop's Warhammer 40K Battlefleet Gothic has been out of print for quite a while now. But that's not a reason to stop building fleets and waging epic battles!
Below are a handful of models with full instructions and parts lists created using the LEGO Digital Designer. They are meant as replacement ships not as showpieces. If you are missing some pieces, try the LEGO Pick-a-Brick web site.