I did a really nice ride circumnavigating Cambridge the other day through loads of villages (the parents live in bottisham). It was a very flat 45 miles with the option to turn back into town at any point so maybe it could suit you. Rough route was Bottisham, Wilbraham, Fulbourn, shelford, some villages beginning with H around the south of town, Madingley, Hardwick, Longstanton, Oakington, Cottenham, Waterbeach, Horningsea, Fen Ditton and back to Bottisham. Only real hill was gogmagog between fulbourn and shelford