I believe the HubOne uses a Lantiq chipset but I have no idea how long it's been on the market, I did try using a BT Smarthub 6 Broadcom chipset surprisingly the max data rates and speed tests were lower than the HubOne, maybe my line prefers Lantiq modems?
Could be the case that Lantiq modems perform better on your line. Though, not all Broadcom chipsets are equal anyway. Furthermore, the
Wayback Machine for WikiDevi suggests there are two variants of the Home Hub 6 - the
A version with the
Broadcom BCM63137, and the
B version with the
Lantiq PSB4395. I actually thought there only Broadcom variants of this device, or perhaps I had forgotten.
An Openreach engineer fitted the MK4 master socket
Ah, so it would have been checked then I would presume.
I'm losing it, looking up a Hubone Router! 
For me personally, it's lethargic, some 10% slower than the Zyxel.
I never had much luck with the Hub One. I've mentioned it many times in the past that it is a trash device, at least it was on one of the lines here. It sync'd in the usual range, but unstable to the point where DLM took action and penalised greatly.
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My advice would be to query your provider about 80/20 and see if they can offer it. Take note of their Minimum Guaranteed Speed, since this is
important - since your modem is giving you a max attainable of about ~55 Mbps now, if attains that after the upgrade, they won't do anything if their guarantee is less than 55 Mbps.
Alternatively, if you want more speed, you could look for a G.fast provider. From your estimates, I could see that the clean range is 174.3-138.2 Mbps downstream. I am pretty sure engineers are still sent out for those installs (you could check with the gaining provider) who will try to fix any nasties with your connection.
Could you please do the DSL checker using your phone number? It looks like the one you provided was from your address.
