So now, you finally state your home is outside the 2-year builder NHBC warranty period!
And it was when you bought it last year, that is you didn't buy from new.
Yet you said on 28 November 2018:
Firstly let me introduce myself. My name is Ivo and I just purchased one apartment from Barratt Homes
So which is it?
How can I be expected to give useful advice if I am not in possession of the full, correct facts?
The NHBC is correct in that they do not offer dispute resolution for anything reported after the first 2-years. They are also correct that the remaining 8 years warranty is for structural issues, but does cover windows and doors. However, your windows are not defective causing damage just allowing noise transference so you are on your own.
You will have to pay for any remedial improvement and maintenance, just like any homeowner now.