Multicast on AVM FritzBox 7490 youview

[#1]

Hi, I have recently ordered a Youview box from PlusNet which arrived on Monday, I was not informed that I needed a PlusNet router.  I currently have a Fritzbox 7490 which also links to my home phone.  I have discovered that the online internet channels do not work on the youview box via my current router, PlusNet have said this is due to multicasting, not something I am familiar with.  Has anybody got their youview internet channels working through their AVM router?  If so what do I need to do to get mine working, ideally I do want to use the plus net router, nothing against it just like my AVM router

[#2]

I found this thread over at Thinkbroadband, you may need their help as it sounds convoluted to setup. http://forums.thinkbroadband.com/dslrouter/4270759-fritz-7390-multicast-settings-for-bt-youview-extr...

[#3]

I have managed to download a backup which I believe I need to change in an editor, just not quite sure what I need to change

[#4]

@ocarrollr82

me neither, that's why I pointed you to the TBB thread.