Terrible. Totally unresponsive and bureaucratic, their customer service is the worst I have encountered as a tenant (and lets be honest the standard in the London rental market is not generally high). We had not hot water for 2 weeks during the winter cold snap and they could not get beyond their processes to deal with it. Each representative blamed someone else. Had to threaten to sue them. Avoid.
What agent could do to change your mind?
Been polite and responsive when presented with tenant issues, rather than evasive, elusive and unhelpful.