I'm afraid Taylor Wimpey have history for sound transference, especially in flats.
They know it will be costly in time and money to find and rectify the problem.
Search Google for "Taylor Wimpey sound insulation" and you will see 20.000 results.
Also search on this forum too, as others may now have had it sorted and may be able to tell you how they got Taylor Wimpey to eventually fix it. PM them.