I had rented a property via Avrasons for 8 years, they also managed the property. Whenever there was any kind of issue (for example, boiler stopped working, fridge stopped working, sofa spring broken, small amount of damp in the hallway from a flat above) the issue was resolved on the same day I reported it, before I'd even got home from work. The issues were also resolved thoroughly so that they never happened again, for example, a new fridge, a new sofa, a full service of the boiler.
Not only was the property management the best I've experienced in London over 20 years of renting, but the agents were very thorough and quick in getting my deposit back to me when I moved out. They also refunded a percentage of rent back to me because I moved out 3 days before the end of the month, this is not something I had even considered should happen!