Name Change

So my partner and I arnt married and don't intend on getting married either, not because we don't want to we just don't see any point, a piece of paper won't change anything to us.  So I was wondering when our baby is born, he wants it to take his last name which I am ok with, however I don't want to have a different name to my baby, so do you think it's acceptable to change my surname by deed poll to my partners last name? It's cheaper than a wedding!