With MyWaitrose card & Pick Your Own Offers pay £2.00 for two packs in-store; effectively £1 each.
These are quite nice, the closest to "real" sausages I've tried. Wetherspoons pubs serve them as part of their vegetarian breakfasts. Don't confuse them with other types of Quorn sausage.
Offer on until 11 October according to the Waitrose site, though they might end it sooner. This is a great price I think; according to MySupermarket best elsewhere is three for £5 (so £1.67 each) at Tesco.