"Lie back and think of England" was cliche' advice from Victorian mothers, but it didn't come from Victoria herself. She was quite frank in her diaries about how in love she was (in every sense) with her husband, and her youngest daughter Beatrice expurgated those diaries after the Queen's death for that very reason.
Sir James Clarke, her personal physician, recorded in his own diary that when he advised the Queen not to have further pregnancies, after her youngest child was born in 1857, she was quite blunt with him about not being willing to give up the physical pleasures of marriage.
Thanks for the info.