You don't need work experience! I do chemical engineering at a Russell group uni and I had no experience when applying and I still don't, I got offers from all the unis I applied to!
In your ps you need to talk about why you want to study the subject, what's interests you about it and why you are most suited for the course! You need to sell yourself to the uni that you are the right fit for the course. You can also talk about academic achievements and extracurricular activities, relating it back to the degree course.