I stayed with Saffron for one year. It was horrible. I moved into a flat full of old foodstuff and it wasn't cleaned properly either.
Once I had moved in, I found out that many things were not working properly, including the loo and the water tank. It took them around three months to get even the most essential parts fixed. Well, in the end I contacted my landlord and he got it fixed himself. I went to the office a couple of times during these three months but that didn't help either. As I said, the landlord fixed it in the end.
I also know for a fact that they lied to me, which is something I don't appreciate: If something does not work as it should, I think it's better to say that a job has not been done but saying that it was looked at that day when it wasn't is something I can't accept from a "professional" letting agent.
I also had further problems at a later date, and again it took them 1 month to get it fixed (this time it related to a gas hob!!!!).
In sum, don't use them. They will drive you nuts and cost you a lot of time trying to chase them, which does not help anyway.