The flaunching as i understand is mortar that holds the chimney pot to the capping. Does the capping look new? They would have had to put wooden shuttering around the top of the chimney stack to 'cast' the new capping out of a mix of cement and sandy aggregate, the chimney pot will have been removed prior. To allow the new capping to set before removing the shuttering then it should have been up two or three days minimum. �20 an hour is cheap for a roofer- you may get 8 hours for �160 inc his labourer if you are lucky - does not sound from the money point of view that your chimney has been capped. Lead alone can be �60 for a small chimney repair.