My current property is through Black Katz Camden office, we have had no problems but other than the day we signed the contract we have had no contact with them as our landlord owns offices in the same building.
The problems started when coming to the end of the tenancy and looking for a new property, we went into the Camden office and essentially got shown out again straight away saying our requirements were unreasonable and no properties would ever become available, even though they had multiple suitable properties on their website.
I then tried the Hammersmith office, on my way to view a property with them when I was practically right outside their door they rang to see if I had received their voicemail (no such message exists) saying the property had already been let and that I was a liar and should buy a better phone by saying they didn't try to contact me.
I did not appreciate being called a liar and as they had my phone number they could've even sent me an SMS as well as the supposed voicemail. I am never using any Black Katz office if this is the treatment they provide their clients and I would not suggest them to anyone.