The spec's not perfect but I think the intention of it is clear enough.
"Intention" and "inferernce" is not enough I'm afraid. Builders are not necessarily the sharpest tools in the box - you need to specify exactly what you want otherwise they might misinterpret what you want.
I always supply a drawing. Here's a very simple one that I supplied to our builder when we were knocking rooms together and redoing one floor (the differences in heights were to accommodate the new finishes giving a level surface across all three rooms).
https://drive.google.com/file/d/1SyvuOBhKOhUqSBVEpss62Vg6ZSXoKloh/view?usp=sharing
An adjudicator would take the view of how a competent builder acting reasonably would interpret it. Personally I see no reasonable alternative interpretation. "Entire garage" can literally only mean the entire garage.
It doesn't matter what an adjudicator thinks if the builder hasn't got any money...
Have you actually checked the trade price of a garage door , or some kitchen units?
Those prices are on the high side , they are on site doing the job with all the tools required. Its a few hours work plus materials .
Re the floor. Can't you just DIY it with a decent self levelling compound like mapei 3240 . Bucket , mixer , float , some packers screw in to the existing to keep it level. Then flaunch in a lip with a bag of concrete.
Less agro than fighting with the builder , let them get on with it . Get them off site and pay . Then relax , no one is going to die if the floor is abit ridgey for the next few weeks. If you don't want to do it then find a one man band who will do that job for £150 cash if you knock up the compound and barrow it into position
