iPhones 5 or 6 won't connect to 802.11n WiFi

So this issue has been frustrating me for days now and I've not gotten any closer to a solution, so here goes,

I have a Belkin N600 DB router which supports dual band wireless N. Any time either of the 2.4GHz or 5GHz networks is set to 802.11n, none of the 3 Apple mobile devices can connect but can still see the network. I just get an "Unable to join network" message. (MacBook Pro and Apple TV both connect fine though). Yet when I switch the 2.4GHz to 802.11g, they all work fine, same with setting the 5GHz to 802.11a. It seems the mobiles don't like anything to do with wireless N.

The 3 devices are an iPad 3, iPhone 5 and iPhone 6.

The Belkin is hooked up to the Sky Hub, (as the Hub's WiFi isn't great), and according to my MacBook, the Sky Hub transmits in 802.11n at 2.4GHz when the WiFi is enabled, and during this, the iPhones and iPad connect fine, no issues at all! So I can't figure out why they can't connect to an identical network setup when broadcasting from a Belkin router.

I'll add screenshots to show the similarities with the Belkin's 2.4GHz N network and the Sky Hub's network, should make it clearer as to why I'm so confused. The channel is the only difference in the screenshots but i've tried switching them round and it doesn't help.

As you can probably guess, the Sky Compys is the Sky Hub network, which the devices connect fine to, and the Home-Compys is the problematic Belkin network.

I'm not sure there's enough information here to help with a solution, maybe it's the iPhones/iPad? Any help would be greatly appreciated, Doesn't seem right to have to use 802.11g with the latest tech. (Also wireless G seems to give me a max download of 20Mbps, on a 40Mbps package, N provides the full speed)

Thanks in advance!