Makro website showing Tilda Basmati Rice, at Park Royal, 20Kg bag for £29.79. Hopefully same price other branches. (works out 1.49 p per kg), but you have to purchase instore. Our friends picked up a bag about 2 weeks .
You very rarely see it under £35 ( £34.49 at Affricarr http://www.africarr.com/store/index.php?route=product/product&product_id=87
). Even more expensive if you buy it by the Kg in likes of Tesco.
Makro also have our other faviourite rice Tolly Boy Basmati Rice 20KG for £21.99 (but more expensive then we usually buy it for. IMHO worth paying the extra few £ to get the Tilda bag).