Final update on this. Install went smoothly today - subcontractor was very happy to use the conduit and drawstring I had provided to install the fibre, so it's in my cupboard with the rest of my comms gear (SH2, managed switch, and patch panel terminating CAT6 to all rooms). Total install time was les than 45 mins start to finish. Various speed tests now showing a solid 920/110 service - my son just happily reported that he downloaded 102GB of game updates from Steam in less than 20 mins. Probably helps that we're the first order on this segment, so no contention to the exchange yet.
A few notes from my overall experience in case they help anyone else searching this in future:
- there was roughly 8 months delay from OR being told poles weren't acceptabe to them clearing the duct and deploying wall-mounted CBTs
- to answer my original question - as others suggested, OR deployed enough CBT capacity to allow at least one fibre per property (probably 10% more)
- time from CBTs being installed to orders being open on BT website was only a couple of weeks in this case
- I put in 20mm o/d flexible conduit with a drawstring (pulled through with a vacuum cleaner) and the technician was very happy to use this to keep the install tidy
- I switched the BT SH2 to full-fibre mode before the install was complete (at the request of the installer) - there was no break in service, as the hub kept using the copper at this point
- once the fibre was fully operational (solid green light on ONT) I removed the phone line connection and it switched over instantly
Last point - the ONT is
tiny, only around 8cm x 8cm.
Thanks to all for help along the way, I'm off to spend the evening running speed tests