Neil Coward wrote:
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.


You may want to have a look at the FIDE Laws of Chess
(http://www.fide.com/official/handbook.asp?level=EE101):

9.1.a
"A player wishing to offer a draw shall do so after having made a move
on the chessboard and before stopping his clock and starting the
opponent's clock. An offer at any other time during play is still valid,
but Article 12.5 must be considered. No conditions can be attached to
the offer. In both cases the offer cannot be withdrawn and remains valid
until the opponent accepts it, rejects it orally, rejects it by touching
a piece with the intention of moving or capturing it, or the game is
concluded in some other way."

The point is that (speaking about your example) White's draw offer is
valid, until Black has moved or accepted or rejected.

On the other hand, White is well advised for next time to offer the draw
along wright after his move, not while thinking about his move.

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"

The arbiter was right and White's friend was wrong.

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

You can change your mind, but you cannot withdraw a valid draw offer. ;-)

Hope this helps, Christoph.