30L bags (~15kg?) of Pets At Home own-brand wood pellet cat litter £5.59 (was £8.99).
You can also order online for in-store pickup. (You need to spend £35 for free home delivery, but possible 2% TopCashback with that.)
Check your bank account offers if you have a Santander, Halifax or Lloyds current account; sometimes they offer cashback on Pets At Home purchases. 10% cashback showed for me.B&M have a similar product
for the same price too.
2017-07-14: Just noticed these are now on offer, 3 for £15.