Sounds a bit unethical. Presumably no one would actually agree to clean the place for 15 euro so it sounds more like a surcharge. I’d contact booking.com about it. I’d also ask for a receipt when/if you pay it which might flummox them. OTOH you might ask yourself if it’s worth making a fuss over...
Yes but if you read through this thread you’ll see that it quickly became accepted by some that it was sit anywhere for us too. Even the misperception is risky so let’s hope the club makes it clear that this isn’t how it will be.