Careful...never trust Openreach. They might have DLM secret for FTTP for residential customers except the business grade.
Okay that is ridiculous.
There is no 'dynamic line' to manage. You connect to the FTTP network at full speed, in the case of GPON roughly 2.5 Gb/s down, 1.25 Gb/s up, and then get a slice of that depending what you're provisioned and paying at, or you don't connect at all - end of discussion.
Building better networks, not just faster ones.