There are poultry sales in Forfar every so often- check the Lawrie and Symington website as they are held in the auction market. There aren't any sales in Fife that I know of, but sometimes there are selling classes at shows in Fife.
The Scottish National Poultry show is next weekend at Lanark market, and there will be a fair number for sale there. Often though, they can be show quality, and sometimes the prices are higher than you might pay at a livestock auction.
Lanark market (Lawrie and Symington again) have a rare breed and poultry sale every month or second month. It's usually on a Thursday, so I don't go very often due to work! The website should give you the details of when the next one is.
Beth