You have a perfect right to a new home without faults.
The Professional snagging inspection will give you a thorough report, which DWH should take seriously.
After all the inspector is doing the site manager's job for him!
I would suggest that you tell the site manager:
1) You will not legally complete on the house until your inspection report are 100% rectified.
2) If the site or the regional office continue to act in such an unreasonable manner write to the Barratt CEO David Thomas e mail
david.thomas@barrattplc.co.ukAs for the pipe, you bought a house built to those plans. If they refuse to move it you can say that you have been mis-sold. Ask them for a letter saying outright they are not moving the radiator and don't have to stick to the plans. Tell them you want this so you can complain using the Consumer Code Adjudication Scheme. My guess is the radiator will be moved.
I must say that this is not the action I would expect from a house builder that prides itself on its customer satisfaction score!