Problem is that they are nailing you on everything, which is a problem, they are nailing you on parts, additives and pretty much everything, they were already going to make a decent profit but they are going on an overkill to get the whole rent for the month on you.
Firstly I would eat my hat if an UP takes 5l of oil, I drive a 1.4l and the most it takes is 3.6l or so, your car is a 1.0l 3 cylinder.
The oil flush, unless your car was not serviced for a long time and the oil turned into a thick gunk, you don't need a flush.
You also don't need an aircon treatment, but it's your choice.
Yes new brake discs need to be cleaned, they are oily, but it's just a few squirts of brake cleaner, you are paying for a brake cleaner for the whole workshop, basically all the cleaners/ additives you buy are for the whole workshop and other cars, not just yours.
I can go on but I am sure you get the picture, they are treating your car like a barn find that is being restored.