set table1.NoOfCars=table2.NoOfCars, table1.NoOfpeople=table2.NoOfpeople
( table1.houseno=table2.houseno and table1.address=table2.address)
(table1.noofcars="unknown" or table1.noofpeoplec="unknown")
note you will have to match noth the house number and street to be sure you get a match.
you may need to extend the query to make sure you are using a common capitalistion appraoc.. ie the where clause may not match Bramhall Lane with bramhall lane