Treforest is a lovely area and my daughter visits Pontypridd every week for the farmers market, indeed a small world!
No one at the organic farm knows about wheat so I asked my B in law. Winter wheat is sown Sep/Nov and takes around a year. Spring wheat is sown around March time and is ready Sep/Oct.
Winter wheat is more popular with commercial growers because of bigger yields. It is prone to all kinds of nasties, the worst one being Septoria (not sure of spelling) which is a fungus. He says the organic growers he knows have to buy the best disease resistant strain they can find.
There is something called a flag leave located at the bottom of plant that MUST be kept clean of nasties (he was adamant about this) other wise the grain doesn't grow properly.
At first he said yields are around 3-5 ton per acre then said no where near that if it wasn't sprayed
I checked where I got my bulk bags of wheat-grains for (wheat grass juice and sprouts) and they came from Doves Organic Farm so maybe they would be able to tell you more
http://www.dovesfarm-organic.co.uk/index.htm
Hope this helps.