Project management can be an extremely difficult discipline because the nature of the work involves communicating with such a wide range of people. Building projects are reliant upon their project manager because it is the project manager that schedules all the work that needs to be done and generally makes sure the project is going to plan.
Some people act as their own project managers when they need renovation work doing on their homes, but this is a risky option. Working with professional project managers is favourable if you want your renovation work done as efficiently as possible and with the minimum disruption to yourself as possible.
Working with a design and build company is a really sensible option, because a professional project manager will be assigned to your specific job. You will liaise with your project manager whenever you need to talk over your project and they will communicate with you and the people involved in your renovation to find the right solutions.
Project managers for professional design and build companies in London also benefit from the fact that the builders and designers they are working with all work for the same team. This is an advantage that is passed on to you via the efficiency of the project.