I was arriving early so Natasa arranged for me to pick up the key from the corner shop nearby which made a big difference to my trip. As it happened someone came before me and collected the key, no idea who it was and the shop owner was worried they might have been trying something dodgy. The shop owner called the police and I went to a nearby cafe - within 2 hours Natasa had driven into Athens, got the locks changed and given me a key - plus some delicious things from the local bakery and many apologies.
The event was just a random unlucky occurrence, Natasha handled it in a very professional and speedy way and as a result it had basically no negative impact on my stay. Thanks Natasha!
The flat is larger than expected and stays very cool compared to how hot it was outside. Great location for those interested in Exarchia and a very comfortable stay.