The other key thing to do to prepare a good geography PS is the thoroughly research the detail of the course content at the universities that you are applying to.
Geography is a degree where the same course title can cover vastly different content so it’s really important to find out what topics are covered at each university (and then to make sure that your PS isn’t talking about moocs or further reading into topics that aren’t covered at one or more of your choices).
Look at the module options at every single one of your choices and possible choices. Especially the compulsory and core module topics.
This is far more important than work experience or soft skills for an academic degree like Geography