You should have detoured into Watermead to grab the two tiles there. One you can get easily via other roads, but the second one it's really the only way to cross it off, so hitting them both on one ride is the easiest way. But at least you did get the Folly Farm tile (opposite side of A413 to Hardwick) which was a pain for me because the first time I didn't go quite far enough so had to do it again!