I have been doing this for years, even in private military companies.
First Option: Install LogMeIn in a computer at home, and then use logmein.com in your work PC Browser to remote access your PC at home from Work PC, works incredibly well an its free.
If you have access to Logmein.com then you are good to go.
Depending on your position, and if somehow they find out how many hits/time/data has been spent on the logmein URL, just tell them you were having a bunch of meetings with Join.me, which is owned by logmein and uses the same kind of URL.
Second option (EXTREME): If you are completely paranoid and dont want to use your work network AT ALL...
The idea of this method is to use your cell phone as your internet connection, in Windows you can have more than 1 network connected to a computer.
Use "forceBindIp" google it... to force a PortableFirefox to connect using the IP of your Cell Phone.
Needless to say, you need to make sure you have a good cell data plan, and also this wont work unless your PC connects to your Works network using an Ethernet cable.
*------------------------
The above cases are extreme, usually you will be fine with whats below:
These are my essential settings/plug ins for wasting time at work
Above all, get FirefoxPortable, dont use the normal Firefox, make sure to install firefox portable to a Flash Drive, if they dont allow Flashdrives at work then make sure you install it in a weird System folder. You will need to tweak a small file to get it to run alongside normal firefox, google it.
TrayOnMinimize (hides FirefoxPortable to the tray area in windows when you minimize)
AutoHotKey (map an extra key on your mouse and TAB on your keyboard to minimize FirefoxPortable, works great when someone comes close to your computer and you need to hide it while keeping eye contact)
ImageShowHide
Foxyproxy
Also make absolutely certain to set up firefox portable to delete all your personal data everytime you close firefox, this will work great if they fire you for wasting time at work.
http://www.howtogeek.com/137681/how-to-automatically-clear-private-data-when-you-close-your-browser/
Usually they will fire you as a surprise and wont let you touch any of the computer equipment after you have been fired, so make sure you close FirefoxPortable every time you get called to your HR, Boss office or pretty much every time you leave your computer.
Have fun being paranoid, completely worth it to get through those days when you just cant work.