Wardy,
I have used the Blight Watch, as recommended by Jerry, for 3 years now and our local BBC station gardening programme gives out the news too
There are also maps on the website showing where outbreaks have been located - a combination of the right conditions and blight in the areas is what you need to watch out for
Phil
Unless you missed it tha last time I mentioned it - most blight outbreaks are traced back to last year's potatoes, either those discarded or volunteers - so if you see any - please dig 'em up