There's one in Wrocław that I know of, and it was VERY expensive.
I know one in Warsaw - it's pretty well empty and only exists because they own the premises (the old 'drying room' in a large block of flats) anyway.
I've had friends do their laundry at my place.
Same here although I know more people who just do their washing in the bath. Sales of the type of powder for hand-washing are high in Poland.
Very common, especially among students and young workers. A lot of young people with oversized suitcases or bags on trains on Friday and Sunday evening.
This is really common, people who rent or even own flats but go home every weekend by car take washing back, don't cook for themselves but just reheat stuff. This isn't off topic, since anyone with an idea for a small business in urban Poland has to take into account this demographic and their lack of ready cash as well as their staying in town only during the week.