I will answer in three parts:
Staircase:
It is highly likely this would have been delivered in two or more parts, perhaps even with a half landing constructed on site. It will be the joining of the parts which is making the noise, from both lack of glue and insufficient fixings. IN addition, it is also not uncommon for the carpet layer when fixing the gripper rods, to knock out the ply risers which do to an extent hold up the treads and if this is the case this would cause a squeak too. Finally the bottom tread is a bullnose this too could be loose.
Floor:
This has been covered so many times before on this forum. Please refer to the previous posts.
If the spans are too great and if joist suppliers instructions have not been 100% adhered to there are many things which would cause the floor to creak due to excessive deflection.
Another cause is the drylining up to the underside of the joists or ceiling plasterboard.
WC:
All SVP boxings should be insulated with sound deadening quilt. You should not be able to hear the WC flushing from either floor in any room.
Given what I have been told about Bloor's poor aftersales, I think you have been very fortunate to get your snagging completed.
Thanks for the reply.
The stairs are a single flight. I'd say about half are creaking. They pretty much always have, except since making my complaint, I can't replicate the fault! I think its, when they have not been used (overnight), and perhaps when it's colder, that's when we hear it. Take onboard what you say about the carpet fitter. Might just leave it. At least it's logged. I have until the summer, before two years are up.
Re the creaking floor; yes I've read from others on here, of the problems they've had. Luckily (or not), it's the landing which has just started to creak. It has a carpet which can be removed. It does creep into one bedroom, which has Kardean flooring (relay-able), but I'm not too keen on having it lifted. Can it be rectified from below?
My other concern is the noise transfer between floors, and rooms with WC. I note its 43dB & 40dB. I've done a simple DIY test with a meter, and get 36dB on both, i.e source room was 72 and receiving room 36. I know the test is a bit more technical than that.
I've read, that the first house of each type should have an acoustic test carried out?
Me and the neighbours were the first of our type. Noted your comment on the soil stack lagging.
I have had 5 houses in my time, only one was not a new build, so I know what to expect. This is the first one with I beams, and metal studwork though.
To be fair to Bloor Homes, they have been prompt with the snagging and done what I've asked, this being a bit more involved though. For example, I reported this problem on Saturday, had a phone call Monday and someone's coming this Thursday to inspect