XL Pack of 70 Ecover Dishwasher Tablets half price in Bradley Stoke (North Bristol) branch. Now just £6.38 for 70 tablets (just over 9p per tablet)
In my experience they only stock the jumbo boxes in big branches.
They also had the small boxes of 25 tablets on offer. £4.70 per box, or 2 boxes for £6.00 (which works out at 12p per tablet).