I want to pull through all project issues into a smart sheet using a JQL query filtering on "label"
Can you assist on the JQL to be used
I'd suggest using the advanced search option built into Jira to build the necessary JQL for your filter. In Jira you can click the magnifying glass icon to search, then select "Advanced search for Jira issues". This should help you build the JQL you need.
Note that if you're using a self-hosted version of Jira the method for finding the advanced search may be slightly different. In my test self-hosted environment, I can find that by selecting Issues then Search for issues.
You can read more about this functionality at Atlassians Advanced Searching article.
Hope that helps!