You can cancel a bid. I did it once but do not remember how it was done. You are free to sell to who you want to sell, or not to sell.
There's a time-limit on to cancel bids. Once the auction gets close to finishing you can't cancel them.
Yes you can cancel up to 12h but someone has bid you can only stop the bid and sell to him.
I have a friend who is signing up on his mobile phone at the moment and will bid if he is fast enough
Thanks for your help, I am not too stressed by this since we are talking about 1cBTC but it is never nice to be scammed