Can you talk to your work It department to get help updating your computer to Firefox 35? You shouldn't downgrade your home computer as that leaves you at serious risk for attack and data getting stolen.

Thanks - I have spoken to them but there is some corporate issue that prevents them from upgrading. The only other browser they use is IE7. Im guessing that it must be a data protection issue (which I dont want to circumvent).

Mozilla do offer an "extended support release" version of Firefox which has fewer large updates than regular Firefox and so is easier for IT departments to support. The current version is 31 - maybe discuss upgrading to this version of Firefox? https://www.mozilla.org/en-US/firefox/organizations/

Another option is Firefox Portable, which you could install on your PC yourself. But be sure to check with IT that this is acceptable. http://portableapps.com/apps/internet/firefox_portable