Went to Superdrug today to see what deals they have on mouthwash and came across this deal.
Purchased 6 x 600ml bottles for £7.98, which works out to be about £1.33 per bottle.
I do prefer to use complete Listerine but couldn't argue with the savings. Checked the ingredients and this one contains alcohol too (for anyone who is interested).
They had another bottle on offer, same brand, but it was for £2.99. I am not sure which or the size of the bottle but i imagine it would be the alcohol free version (could be wrong).
It is no online so instore only.