@Armin39 Guests who willfully deceive you, violate your rules, steal your property, or overstay without your permission are taking advantage of you.
But it's not the guests' fault when their host agrees to requests that they're uncomfortable with. In this regard, it's important to remember that good hospitality does not mean "whatever the guest wants, the answer is always yes." Rather, I'd say it's all about delivering well on everything that your listing offers and being resourceful with advice for wishes that aren't inclusive.
Fortunately, you're in Central London, where virtually anything a guest can want can be found. If they're arriving before your check-in time, you can suggest a free museum, park, or brunch spot to enjoy the time before their room is ready. Need storage for bags? Forward them this list of storage facilities: https://www.visitlondon.com/traveller-information/essential-information/baggage-left-luggage
Need a shower after checkout? Have a recommendation on hand for a local pool, spa, or Turkish bath that offers an affordable day pass. The same thinking can go for any amenity that they need outside of your time and scope of offer, and most guests will be pleased that your local expertise led them to a unique experience. If you find yourself bending over backward, it doesn't mean you're making guests more welcome, it just means you need to see a chiropractor.
As for the towel situation - it's actually a frequent complaint of guests that they couldn't figure out where to hang their towels, so be sure that your check-in tour includes instructions about where the wet towels go.