Quick help needed, please!! How can I sell to someone who wants BIN when listing is auction format?

[Tinkjon]

I'm selling something which was only listed as an auction format but somebody hs just asked if I'd accept a Buy It Now price, which is a very good offer! I can't seem to add the Buy It Now option though, is that correct? (the item already has bids, maybe that's why?)

What would be the best way of doing this, any ideas?

Actually, I've just Googled and seen that ht eonly way to do this is to cancel bids and revise the listing,. that's not really ethical though, is it? Is it acceptable to cancel other people's bids? (I know it's technically allowed, but still - doesn't seem fair).