No sovereign after around 1850* is worth much more than melt at present, well a small premium maybe for the fact that it is already in an easily traded form like bar. Currently any Sov can be sold for around £325 if you go to the right people. I would flog it and get the watch, unless you think gold has much further to climb.
*yes there are some rare ones minted in the colonies and rare years that may be exceptions but in the main they all get melted when the price is as high as it is now, I know some bullion dealers personally so have an insight.