This sounds like Content Security Policy hasn't been configured as per https://wiki.jenkins.io/display/JENKINS/Configuring+Content+Security+Policy - are you able to give that a go and see if that fixes things? (Please note that it will only work on new HTML reports not previously created ones)

Thanks, that has worked (Should have looked at that first, apologies), happy for this to be closed, thanks for the help

All good - its sometimes hard to spot. This comes up quite a bit so was wondering if there is a particular place that you think it would have helped to have it pointed out clearly to make sure that you have the correct settings? (e.g. the Wiki page, the Github page, somewhere else?) 

I think (for me) there was a lot of information (slightly overwhelming) but probably necessary due to the possible consequences of making changes of this nature.

In the end i found an answer on StackOverflow that pointed out that changes could be made directly in the Script Console setting 

System.setProperty("hudson.model.DirectoryBrowserSupport.CSP", "default-src 'self' 'unsafe-inline'; style-src 'self' 'unsafe-inline';")

This was the only way i could get the inline scripts to run (not saying this is the best way mind)

Thanks - will continue to look at ways of making the CSP stuff a bit more visible to avoid this in the future but, in the meantime, glad to hear that you are all up and running.