Vanquis cash transfer to current account

I received an email from Vanquis a few weeks ago offering me a cash transfer to my current account with no fee and interest charged at the standard purchase rate. Am I correct in thinking that if I was to take this option then pay off the card in full before my next statement I would pay no interest as is the case with card purchases?

The purpose of this is for stoozing, I would pay off the Vanquis balance by transferring it to the Sainsburys card I've just been accepted for then transferring the cash into a savings account.