First of all name the housebuilder!
Friday 21st December is the absolute last day for legal completions for many housebuilders end of year or half year's figures. Your home is being rushed and I would guess in all probability will be no where near complete for you to move in on 21st December 2018. If you do, you will have no end of problems trying to get unfinished and sub standard work rectified in the New Year and beyond.
Please get your home professionally snagged and inspected before you legally complete, or at the very least check the home the day before.
Do not legally complete if you are not happy!
It is my opinion that far greater work is required than you stated or were stated in the letter your are being asked to sign. I doubt very much that any warranty inspector would withhold a completion certificate (CML) for scaffolding in a rear garden and a temporary fence.