If there is a Woolworths clearance store near you it may be worth a visit.
I went into Slough as a friend said they are clearing Dulux weathershield paint.
In short the 6L cans are £5, the 5L cans £3....but 50% off clearance = £2.50 and £1.50
I took what was on the shelf, 17L for £6.50
lots of other things available, not just diy all 50% off already marked down prices.