This deal appears to be in-store only, but when I went to the Handforth Dean store this evening they had loads. Possibly end of line, but is very cheap for 20 washes (5p per wash!) if you're nearby. Will upload pic of receipt for proof.
Cue forum members posting pictures of geese and other assorted jokes about Tesco deals. When it comes to Tesco, the way I see it, some you win, some you lose. I have missed the last few, but have stumbled across this one!