Yes, you are quite correct. It should read: "TalkTalk uses DHCP to obtain an IP address and not PPPoE as most other ISPs do." But I think you understood that :)

My sync speeds on VDSL2 have been very stable for the last 84+ days so my calculated figures will stay the same for some time, I would like to think. My DS sync speed is 58976Kbps and thus I have calculated a reference value of 58068Kbps based on your formula. The US sync speed is 10422Kbps and the reference value for this is 10261Kbps.

Setting the reference values to 50%, I have: 29034Kbps for the DS; and 5130Kbps for the US. I will test with these numbers shortly. Am I right to assume I can just paste these into the SQM interface on LuCI? I will set the "Queuing discipline" to cake and the "Queue setup script" to piece_of_cake.qos.

I assume also at this stage, to set "Which link layer to account for" as none (default)?

I will then increment the values I have pasted into LuCI (assuming that is correct) as you have said. At this point, with an assumed overhead of 8, do I just choose Ethernet with overhead... and then set the "Per Packet Overhead (byte)" to 8?

Is there any benefit of going through UCI?