I note that the expression, ""Broadband circuit Service ID", occurs on the BTW Diagnostics Tests, in the "Further Diagnostics" section -

http://speedtest.btwholesale.com/

Although shown in the FTTP section, I wonder whether it does exist on ADSL and/or FTTC circuits?

Possibly someone with greater knowledge of the "behind the scenes" of broadband could give an answer.

No one seems to have broached the simplest explanation - the PlusNet portal and usage tracking may be attributing usage wrong

As broadband circuit service ID yes these do exist, and given the way phone numbers are virtual are needed to identify circuits

In reply to a post by MrSaffron:

No one seems to have broached the simplest explanation - the PlusNet portal and usage tracking may be attributing usage wrong

As broadband circuit service ID yes these do exist, and given the way phone numbers are virtual are needed to identify circuits

Was just about to post this.

Evening Andrew.

So this possibility seems similar to the allocation of "Presentation Numbers", in place of the normal CLI numbers.