In your OP you said you had set the gateway to .254 ... which I did not take to be the HH.
So, set the HH to 192.168.1.220 and save the configuration ensuring that DHCP is off and HH not connected to anything.
Reboot the HH, set your PC to 192.168.1.10 (or similar) then, connect PC to HH and using a browser try to access 192.168.1.220. Once you can do that, disconnect and power off the HH.
Connect HH to the O2 box and then power up the HH.
Connect PC to HH (by cable) and try to access 192.168.1.220 - which should be possible and then 192.168.1.254 which should also work.
If not, I wonder if a Changeover Ethernet cable is required?
If it does, connect to the O2 box and try to access .220 again.
If that works there is nothing local and you may have a firewall issue.
M H C
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