Christie, much has been said about Ennis being a "one's enough" man. However, I have known enough people who have loved deeply, lost tragically and recovered to love again, just as deeply - to believe that Ennis has fallen in love again, deeply and completely, with Ellery.
He has awakened to his awareness of his attraction to males as his denial has decreased, but that is just what that is - attraction. It doesn't mean he is truly drawn to any of the men he finds attractive, just that he is no longer denying that he sees and appreciates other men. It is a measure of his growth and coming out. I believe his attachment to Jeremy is a friendship between men. For Ennis, his awareness of his physical attractions is still new, so to the seasoned eye of Jeeves, he might have noticed Ennis gawking, particularly if his own laser beams were fixed on Dupree at the time. But remember, it wasn't Ennis who dreamed about being in bed with Dupree - it was Ellery!