Boys:
William - really like it. Timeless and Classic
Benjamin - like it
Oliver - not keen but I don't know why. I think it might just be personal associations with people I know with the name as it's obviously a perfectly nice name!
James - quite like it.
Nathan - not overly keen but do love Nathaniel.
Girls:
Christiana - quite fussy. Prefer Christina
Sophia/Sophie - really like both
Katherine - really like it
Anna - really like it
Sylvia - quite like it
It sounds like you have quite traditional taste. How about:
Adam, Andrew, Alexander, Benedict, Charles, Christopher, Callum, Daniel, David, Elliot, Frederick, George, Henry, Isaac, John, Jonathan, Joseph, Joshua, Jacob, Jack, Luke, Lucas, Matthew, Mark, Michael, Nicholas, Oscar, Peter, Paul, Patrick, Richard, Robert, Samuel, Simon, Thomas, Timothy, Vincent, Zachary.
Amy, Alice, Alexandra, Abigail, Bryony, Beatrice, Bethany, Charlotte, Caroline, Caitlyn, Chloe, Claire, Emma, Emily, Eleanor, Erin, Esther, Frances, Francesca, Florence, Fiona, Grace, Georgina, Georgia, Hannah, Harriet, Isabel, Imogen, Jessica, Joanna, Jennifer, Julia, Juliet, Katie, Lucy, Leah, Lydia, Madeleine, Miranda, Matilda, Melissa, Miriam, Natalie, Natasha, Nicola, Nicole, Olivia, Rebecca, Rachel, Sarah, Samantha, Stephanie, Victoria, Zoe