I lowered the mast with the ginpole. Worked great. I used the spi halyard as a safety,
main halyard attached to the ginpole,
winch to do the work,
strapped the rear crossbar to the slipway,
and just for backup I used my main sheet and blocks attached between the bow shroud and front bridle in case the winch didn't work.
I used the trap wires for anti-sway but it wasn't necessary as there was no wind.
I attached them and the gin pole side stays to the crossbar by sticking a pole into the crossbar.
It was so easy, that I raised it up again. <img src="http://www.catsailor.com/forums/images/graemlins/laugh.gif" alt="" />

Not sure the trap wires were necessary as they were very slack as the mast went down and swaying wasn't an issue.
Also found that by using the main halyard (tied to the ginpole) this kept the mast sideways because it is attached to the rear of the mast and naturally pulled it sideways. Although I did have the mast follower attached to the ginpole via a piece of angle iron. This I think was overkill.

Thanks everyone.