Whoops, just found the 5ghz section, where I can disable it, sorry.
You don't need to disable the 5Ghz frequency just try giving the 2.4Ghz and 5Ghz frequencies different SSids (names). Just add a 5 to the end of the 5Ghz SSid so you know which is which. Check the 5 GHz Sync with 2.4 GHz: is set to NO.
You'll need to connect any of your devices that can use both frequencies to both SSids if you want them to be able to use both frequencies.
See this link
If you can not update the drivers on your Network cards you could change the Homehub to transmit on b/g only which might help.
See link how to do that.
Well, this is wierd! I have just checked my wife's laptop and hers is 'n' enabled. It does not actually say that in Device Manager, but if I go to the advanced section, it states, on one line '11n', so I am presuming it is.
I then borrowed the Edimax dongle from her computer and slipped it into mine. The download now is instant, even iplayer is working 90% okay. Then I disabled 5ghz and the iPlayer started stuttering again, changed the 5ghz back on again so both that and 2.4 are shared, and the picture was back to normal.
Just need to sort out why my wife's is slow, as hers is already 'n' enabled.
When using the wireless dongle on her computer, make sure that the on-board wireless card, if it has one, is turned off. This is usually done by pressing the Fn/F2 or similar combination of keys.