If it was reported to the builder (please name and shame!) then you are still covered by an NHBC warranty and the builder is still on the hook.
Trouble is it is now a long time without being fixed.
My guess is, if you are successful with the NHBC and they cannot get the builder to fix these things, they will only be prepared to offer you a cash sum to cover the cost of the work, not actually organise and employ a contractor to do it.