Don`t do it mate!
Your ZS looks ace in black & with the big boot spoiler looks the part, its a backward step in my view to come from a face lift ZS to a Rover 45...even if its a 45 V6 it just don`t hold the appeal that an MG has!
Also when it comes time to sell it surely an MG will be more sellable in the future than a Rover 45?
Just my 2p`s worth, your choice though mate!