FTB waiting for completion, credit card balance transfer before completion

Hello, we are FTB (newbuild) and done the exchange phase. We are waiting for completion now. I've just paid deposit for our flooring (not through developer) of £1.6k using my credit card. My other credit card has a promotion now for 0% BT, I've thought why not. Now I'm unsure if that's a good idea. Lender is Virgin through broker. Do you think this is OK? I can pay full the transferred balance if it helps to make things better. We are expecting to complete this month by the way (SDLT).

First post to ask question, sorry if I missed any glaring details.