No worries, appreciate you posting back.

It's easy to miss stuff

To rub salt into wound, Zen marketing sent me an email saying my number is now enabled for fibre. Proceeded to click on the link to order, and nope, no fibre still. Gave Zen a ring for clarification, and after putting me on hold, and finally getting customer services to speak with me, they are now trying to get answers from Openreach. So we'll see what happens next. Will revert.

I concur with @lee111s as to the next steps: contacting Openreach directly, while also getting the ISP to act. And, if these don't work, getting the CEO's office involved, and possibly the chairman as well (though I'm not sure if complaining via the new Openreach chairman, rather than the BT Group chairman, works yet).

When my line had the wrong cabinet number, my ISP (Plusnet) needed to go through a lot of coordination with "their supplier" (Openreach directly, I think, but it might have been via BTW) to sort things out.

When things eventually got sorted,the path was straightforward: there was an engineer visit to just perform a "pair prove" task, in which he identified all the node & pair identities at the DP, PCP and in the exchange. This translated into updating a database known as ROSE. This took an extra couple of days after the visit.

Once the backend database was fixed, it took time to filter through into the publicly-available checker - presumably because it does overnight batch updates.

On one overnight update, the address checker changed first, but the number checker remained.

On the next overnight update, the number checker updated.

On the next day, Plusnet cancelled the old FTTC order (because it keeps the old cabinet identity, even after the checker changed)

On the next day, Plusnet placed a new FTTC order ... which went through fine.

Thank you for replying and sharing your experience. Zen said they will update as soon as they hear back from the supplier (I guess Openreach). There is also an open "case" with Openreach directly.