We stayed at Ουρανία-ζωή place for 3 days. It's perfectly located for exploring Thessaloniki! The apartment is dated, but it is functional, spacious and it was very clean! From the downsides, I only found the bed not comfortable (hard) and very squeaky. However, there were several sleeping places in the apartment and possibly others are fine.
The host was great, she responded to every message with no delay, provided clear instructions on check-in and helped with everything else.