I'm afraid I have to say that we were not able to get into the apartment. The keys were not in the key lock box when we arrived for doing the check in. After calling the Altido Scotland property management agency, they said that they were not managing the property anymore, and offered us other options to stay. This was quite unexpected, given that the communication with them was all the time very smooth, polite and they sent us all the instructions to get the keys.
Although the other flat where we finally stayed was very nice, and we were properly reimbursed with the difference in cost, we consider that still it was a irresponsibility of the owner Harry and Altido Scotland to be offering a property which was not available for rent. We were very lucky in arriving in day time hours, on having the help of one of the neighbours in trying to contact Henry and on being able to talk with the Altido agency in working hours.
All in all, it was really a shame, because the flat in Thristle street was located in a nice area, lots of pubs, restaurants and shops around, and conveniently close to reach the train station and city centre just by a 10' walk.
I hope that this situation can be resolved for the benefit of future guests.