If you care what Openreach ask developers do *now*, you can see their design rules
and their developer's guide
That guide covers a lot of the new requirements for ducting for FTTP, but they've only been in place for the last year or two (and even a year ago, they weren't as comprehensive as they are now). You can bet that a site plan from 5 years ago would only incorporate the requirements for a copper network.
Given the amount of time, you are likely to have been hit by one of two problems in the commercial rollout: 1) That BT's planners didn't include your cabinet because, at the time of their plans, it didn't have enough properties to qualify for the commercial rollout, or 2) That ongoing development of the site means the roads have not been adopted, but BT needs access to perform roadworks. As adoption can be a convoluted process between developer and council, the developer is likely to refuse requests for the roadworks until adoption has completed.
The former is best dealt with by raising the issue with your council's BDUK section. The latter is best dealt with by persuading the developer - but you might find you have no leverage there now they've sold the last plot... they will just want to get adoption finished with as little outlay as they can get away with - but it can be years!
Your best point of contact might be through this contact page