The quality of a detailers work is not defined by the fact that they arrived at your location any more than it is if you were to drop your vehicle of at their location for the work to be carried out. Some people will say that a fixed location is cleaner, this may or may not be true. But if your garage is clean or I clean it and have the door closed then we are both working in the same kind of environment. The end quality of the paint finish is more to do with the products and equipment used and the skill of the detailer who is carrying out the paint correction than the physical location of where the vehicle was detailed.
BMW paint is pretty bad for this, the paint texture resembles that of an orange and is caused by a number of factors typically the result of improper painting technique, quick evaporation of thinner, incorrect spray gun setup (e.g., low air pressure or incorrect nozzle), spraying the paint at an angle other than perpendicular, or applying excessive paint.
The only way to remove this is by wet sanding the paint, some people will tell you it can be removed by polishing with a rotary, this is incorrect as the soft foam pad will conform to the peaks and troughs of the orange peel. Wet sanding is a long expensive process so it may be easier to just live with it.
Swirls are pretty common on paint and can be easily identified, they look like a spider web and radiate out from a central point, they are usually more visible on dark coloured paint and especially in bright sun light or under filling station lights at night. Swirls look terrible, they take away the gloss and usually cover the entire car. But they can be safely removed as they are usually shallow and only in the clear coat. It is simply a matter of polishing them out, however its better to try and avoid getting them in the first place.
Hazing is a patch of dull paint, typically this is caused after compounding to remove other defects. Compounds tend to contain a lot of fillers and if not removed by a good panel wipe will hide defects until it is washed or wears off. Hazing can easily be removed by a finishing polish and is nothing to worry about.