I understand this isn't probably going to get hot but checked two stores today the shop assistant said they're discontinueing the colour so selling them off to make room for the new ones (though not sure if this is true or not.) So it could possibly be nationwide.
They had hundreds of 10Litre tubs of Calico and Hessian which were in the clearance section. They usually retail at £30-£40, and the 2.5litres are £16! It was down to £20 which is a bargain alone, but due to the 20% off dulux paint currently on at the moment it came to £16! I
The stores in mention were Manchester Fort, and Stretford. Although manchester fort had a lot more. Not entirely sure if this is nation wide but if your on your way there its worth a look.