Getting funding is generally the difficult part for getting a PhD in Cambridge. If you do not have any potential source of funding, please have a careful reading here where you can find the different possibilities available. In order to receive funding from the University, you will need to demonstrate an outstanding GPA and reference letters, showing that you are among the top students of your cohort.
There are different postdoctoral fellowship opportunities in the UK. Below is an overview of different calls; they vary in remit, duration and eligibility. Below is a list of postdoctoral fellowship opportunities: