The floor of my daughter flat is sqeaking really badly. We have screwed down the boards to the joists put talc between all boards covered the whole floor with hardboard the noise is still as bad. We have a grumpy downstairs neighbour who is continuing to moan. Have you any ideas

That floor was noisy before you bought so the neighbor has lived with this already for sometime. Exactly what kind of flooring was there, how you spaced your scres and type of screw and what kind of hardboard was use. Was the HB nailed, screwed glued or all of the above