How much time do you spend traveling on your daily commute to work? How much your annual train or petrol expenses? Imagine how mush more productive you could be if that time could be spent working or the money saved used for the family instead.
Instead simply getting up having more time to spend with the family at breakfast, then strolling to you garden office sounds like a much better way to start the day then packed rush hour trains and traffic. Not just gaining time but resulting in a better more constructive frame of mind.
A garden room is private from the house to, away from the busy environment of the office or family home, your be able to get on and achieve more from your working day.