Thanks poj, interesting to see similar issues experienced with ie9. We're fairly locked down here and incognito mode is disabled on our chrome version so was unable to test that. Did test with many more users though and it does just seem to be an issue with ie9 so I'm going to chalk it up to that.

Have just heard there are plans to upgrade that site to ie11 in the not too distant future, so will stick with it for now as the perl solution is quite neat compared to getting a full web server installed for this. In the meantime perhaps I'll check the browser version and point those users to chrome or something!

Thanks again!