Just released from FW is the Castellum Stronghold. The basic board is £90 and is full of detail. I met the designer at the HH weekender and saw the initial mockup, his intention was to allow chapter rhino doors to be used to denote legion specific bases. I don't know whether this has translated into the finished thing but it sounded like a cool idea.
FW are also doing a battle ready version (seen above for £160) with loads of turrets that fit into slots on the board. By my calculation you actually save a bit of money doing it this way and it's very tempting! I've slapped it on my Christmas wish list along with Angron, Fire Raptor, MkIV Assault Marines, Land Raider Achillies, IA 9&10 and a Sicarian. I can always dream!