A friend of mine inherited a house from his dad about five years ago, with his girlfirend he later bought a new house and they did not have to pay satmp duty as they were considered first time buyers, deeds and mortgage in both names. I remember asking him if this was possible at the time and he said he was told it was as he has not bought the house from his dad.
It soounder a bit sus to me but there you go, no one has chased him for any stamp duty, so I guess he was right.