Since the letter Q was chosen as the letter to identify, start your search on page Q-1 in the Serif book. You think it might be font #150.1 which you found on Q-3. To verify your choice, choose another letter to confirm that it also matches. For the letter u look on page U-3; it will be in the same position as you found the Q on page Q-3. If you want to see the entire alphabet, IdentaFONT provides a Composite Fonts section in the back of each book.