Communication was very poor. They probably don't speak English well, because when we got there we took the key out and it was written 1 and the apartment letter. From this we thought it was the first floor but the flat was on the groundfloor, from this we had a 20 minute suffering over the phone but they couldn't help us. Eventually we realised we were on the wrong floor, unfortunately the owners didn't know what the problem was from this, just that it wouldn't open the lock which was obviously the wrong door. It would be worth marking the groundfloor separately for the guest to avoid any misunderstanding.
Overall, the small apartment was fine, heating can be solved with separate air conditioning.