The following happened in a rapidplay yesterday.

Its white to move, white offers a draw. Black says well make your move and I
will think over your draw offer. White makes his move. Black thinks for a
few minutes then says "ok I will accept the draw". White now says the draw
is no longer on offer because I've moved.

The arbiter said white had to accept the draw having offered it. On top of
that Whites friend came along and said he could have played his move and
said as he played it "I withdraw my draw offer"

So what is the position about offering draws and changing your mind?