The new firmware doesn't appear on the TP-Link support site yet. Hopefully it will soon along with some comms about the disappearance of band selection. Seems strange when it was working well. Hang...

@Nevsie Impossible to say for sure, but given discussions on other forums about Three where people use routers from other manufacturers, I think we can be confident Three has network/congestion...

@Piersandro Yes, this worked for me too. It did retain settings though.

@Piersandro All 4G routers are fussy about their position and getting a good signal. I move my router by millimetres and it can affect the signal statistics a lot. This is why being able to fix bands...

@JoshVDH Yes, it is very annoying and something you only find out about once you have a SIM card and find you get good speeds..... and then realise gaming doesn't work! You will be ok if the VPN...

And it appears that Smarty also fail to give you a unique IP, so Three is your only option in this regard.