Cannot connect to Xbox Live parties

[#1]

Sorry if this has been asked before, I've tried a search and can't find anything similar.
I have just moved to Plusnet from Talktalk.  When on Talktalk my router was in the living room, xbox upstairs connected wirelessly, and everything worked fine.
Now I have had to move the router into the hallway because the signal to the xbox was so poor, and my son is telling me the connection is incredibly slow (despite paying the extra £5 a month for gaming) and it just will not allow him to connect to an xbox live party at all.
Are there any settings that are different on Plusnet to Talktalk.  Is it the type of router (Technicolour TG582n)?  Or could it be something else.
I am not technically minded at all, so I would appreciate an idiot's guide please 

[#2]

Sorry we missed this one.  Will get someone looking at it tomorrow for you.

[#3]

Hi there,
I guess from what you're saying the xbox connects wirelessly - is there any way you could test it with a wired connection to see if that makes a difference? Also, do other devices (PCs, phones etc) have difficulty connecting?
It might also be worth trying out http://community.plus.net/library/gaming/increasing-gaming-compatability-with-the-thomson-tg585v8-xb... to see if that helps.
Please let us know if that does make a difference and we'll see what we can do to sort this for you.

[#4]

Thanks for your replies. 
I actually got in touch with the help centre direct when there weren't any replies, and it turned out to be something to do with channels, and they gave me instructions on how to change them.
Thank you anyway