Using Icotera i4850 as own router

[#1]

also changed the physical setup so the Icotera WAN port now connects to the LAN port on the Hub One, with the Icotera just NAT'ing it's traffic out towards the Hub One. 

That wasnt quite my idea. In your configuration you will have a double-NAT i.e both the Icotera and Hub one will be applying NAT. Its undesirable but may not be a problem in your situation. If you use voip or need to do any portforwarding then it will be problematic.

My idea was to leave the connection as LAN-LAN with both the Icotera and Hub one on the same 192.168.1.x subnet, but to move the DHCP function from the Hub one to the Icotera but with a default gateway set to the Hub one.

[#2]

Yeah aware of double NAT, actually plugged it in via the WAN port to test some parental control settings that didn't seem to be functioning properly via the previous setup, but work via this one. Got no VoIP or portforwarding config set up so not an issue there and this is the only way I got parental control working on the icotera though (webUI and functionality of it isn't great tbh)

Did try your setup before with LAN>LAN and DHCP on Icotera with DG of Hub One and that also worked well, not too difficult to revert back to that if I run into any issues down the line so am safe either way (saved the exact configuration)!

Thanks @MisterW 

[#3]

Yes, any parental control functions on the Icotera, I suspect, are only going to work when its in full routing mode