OMG! Good luck with your major headache, BW!!
total example of the scary consequences of 'due diligence' when buying property eh!! I would have cried if we got caught out by that once we settled on our land. Probably similar to Dawn's light pole in the middle of her frontage.
As Tribe has said.. hopefully the cover is traffickable.. it means you won't need to move your house (or worse... pick a new design!) And yes the driveway could go over the manhole...
Fingers crossed you get to a solution that will work for you guys!