Just something to have your friend check out at the home location of the Slingbox.
Have your friend go to setup.slingbox.com on a computer on the same network as your Slingbox and click on "Get Started". Once there, click on "Set Up Internet Viewing".
The following is an image of what your friend should see:
This will test out your router settings, and if it passes, you should be able to watch on your all your devices including your PC. If for some reason the message shows up as almost complete or unsuccessful, you may have to have your friend port forward your router.
The following link is where you can find information on your router if you have to port forward it:
If this still does not work for you, have your friend contact UK support at (020) 7294 0157.
Hope this helps!!
Sling Media Moderation Team