The best way to check when its avainable is use an automated checker, see this post for details. Simply set it to email your phone, and however many times a day you want it to check.
Sometimes it does give an estimated date and a message and other times it does not. Suspect that the available removal is automatic and adding the estimate for clearing capacity issue is a manual process, hence a possible gap.
When I was signing my sister up to FTTC (Via Aquiss) it was the same thing but was slightly different as you posted hippy. The checked (I used the phone number) kept saying spaces we're available but the order failed a few times as the BT checker was wrongly saying space was available (but turned out it wasn't) eventually it did come good for her (on new year's eve funny enough) but eventually it did get put on for her (also on cabinet 90)
Just a question for people in the know (I assume I know why) but notice BT Openreach have been busy recently in Blackwood again (wondered why half the road down the bottom of the estate was dug up) I noticed a new fibre optic cabinet getting made. Would that be due to demand for the service?