Stabilex

[Finn]

Or alternatively just get your black bucket with pva pre-mixed b4 you turn up, tell them its what ever they're expecting it's supposed to be. If it's so supposed to be coloured, get some food die, if it's supposed to b grit like, throw some sand into it.
and if they ask where the product tub is, just say that conviently you had another job prior and that was left over

 

[Wayners]

B & Q. Wickes. Both sell external stabiliser which is now waterbased stuff. It dose say not for internal use however it's the same stuff. Looks, smells and white ish in colour and ment for chalk surfaces. I am convinced it's the same stuff just badged up differently. Sandtex exterior primer is the same again and the tile primer although that is coloured and a bit pricy. It's all a polymer sealer.