I have had 4 BMWs and know them quite well, although not had a 3 series…However i do know that the 330d should return almost at least 40mpg, depending of course on driving style. My ster in law had an older 530d and they got 38 out of it. The 330d is a prper quike car as well.
As for the 2 bikes, they`ll go in no problem with seats down.
Hope this helps.