Taylor Wimpey have history and it seems they trot out the same old fob off, to anyone that complains about sound transference.
See this post!
http://forum.brand-newhomes.co.uk/snagging-and-defects/noise-issues/msg5131/#msg5131So many Taylor Wimpey buyers have the same problem perhaps you should form a WhatsApp group!
Flanking sound is not via up or down. "Flanking is sound that transmits between spaces indirectly, going over or around, rather than directly through the main separating element. This can allow sound to transmit between spaces even though the main separating element itself provides good acoustic insulation."
Re the NHBC it is not about winning, it is about whether your claim is valid. NHBC is an insurance that your home has ben built to the warranty standards. In most cases if there is a fault it has not been. That is not to say the NHBC will deem your claim valid as they have a reputation for batting away new home buyers claims.
Write to Taylor Wimpey and tell them that if they do to begin investigations in the new Year you will be making a complaint to the NHBC and then do just that if nothing happens.