Who, when proposed to by Henry VIII refused by saying something on the lines of "I'd need two heads."?

It was Christina of Milan. Reportedly!

http://www.pbs.org/wnet/sixwives/meet/ac_handbook_...

PS: I don't think Henry was in love with Christina. She was just another contender for the post of Wife. If anything, he favoured Jane Seymour as she was the only wife who gave him a legitimate, surviving son. Unfortunately, she died just a few days after giving birth, probably from the common childbirth fever. She was buried in St George's Chapel in Windsor, and when Henry died he was buried with her there.

http://www.tudorplace.com.ar/aboutHenryVIII.htm

Sybaris is certainly correct. You are confusing two stories. Henry VII considered Jane Seymour his one true wife. The cynic (like me) would say that Henry said this because she produced a living son, and she died before he could get tired of her.

I believe that she was French and her name started with M--maybe Marguerite. I never heard the rest of the story. He seems to have loved Katherine Howard until he learned about her past (and present). and Katherine Parr was with him when he died. Of course those facts don't preclude his being fascinated by the one woman who ever turned him down, and it's not unusual to become convinced that the one that got away was the best of all.