Just came from Poundland in Harrow and they had a big sign of 10% off dental products. All Toothpaste/ toothbrush and mouthwash at 90p.
Just checked online and the same offer is available and so Nationwide deal.
Just 1 example. Colgate Sensitive. 90p in Poundland.
Plenty in the Harrow Wealdstone store.
Deal button will take you to the mouthwash deals for 90p