And all options of the BT Wholesale checker return "line supports", (if it does), not "is enabled". So my phone number was showing the expected speed months before the cabinet was installed.

Postcode Checker Returns
Our test also indicates that your line currently supports a fibre technology with an estimated WBC FTTC Broadband where consumers have received downstream line speed between 31.6 to 35.9 Mbps and upstream line speed between 12.6 to 14.1 Mbps.

Address Chcker does not return any fibre option at all... Go Figure

Looks like I will wait and see what changes over the next few months

If BT have implimented it properly it should be accurate.

The current BT checker on their Web site uses the full Postcode which can cover a dozen or so premises but then asks for the house number so in theory it should be very accurate.

You're referring to the Address checker rather than just the Postcode checker which doesn't narrow it down to a particular property