As far as I saw, the company has an unusually high employee turnover rate. I think that this is why:
The workload is immense and daunting, and you often feel like you don't have thorough enough training to deal with it. In my experience, asking for help with this was actively discouraged by an office manager.
The nature of the role is incredibly stressful and has had a significant detrimental impact on the office as a whole. People seemed to dread coming into work and answering the phone.
The pay doesn't come close to reflecting the workload or the knowledge/skills necessary.
In the Manchester office, there is a very toxic culture, seemingly instilled by office management. Employees going through mental/physical health issues are often made to feel like inconveniences.
Specific senior figures have acted in ways that were deliberately exclusionary to specific employees.
There is a lack of flexibility, such as working from home, to those that are struggling.
A lack of HR means that sensitive issues are passed on to those who have little relevant training. You can tell they're making it up as they go. Not necessarily their fault, but a structural issue.
As another reviewer said, having free fruit at breakfast time doesn't make a healthy office culture.