Help on my topic (Water Fluoridation) - Should I include primary research?

My title is "Should Water Fluoridation be Mandatory in the UK?" Do you think it would be relevant to get interviews from dentists and their thoughts on this? I was also thinking about reaching out to treatment plants, organisations, experts, etc.
I need to submit my planning review soon, and I need to decide how / what I will gather my primary research on, so I was wondering, is it possible to get high marks in the EPQ using only secondary research? Will I be at a disadvantage if I don't include primary data?
I'm not sure if it will be worth doing this though as it will be difficult and I know you can base your EPQ completely on secondary research, so just looking for opinions.