Checkout takes payment and records the address, the plan, the install type, and the router. The line is not live at that moment.
Provisioning
After payment the order is provisioned with the wholesale partner. Broadbent Network keeps you informed of the appointment window.
A go-live date is not fixed until the network operator confirms it. Lead time depends on the network, any wayleave, and when an engineer is free.
The appointment
Someone needs to be at the property to give the engineer safe access. The visit matches the install you ordered.
If nobody can give access, the conditions are unsafe, or the appointment is cancelled without reasonable notice, the visit can be charged as an aborted install. The charge is the wholesale aborted-visit rate, passed on at the retail markup.
When it is live
The circuit is ready when the network marks it live. Where the plan includes a static IPv4 address, it is assigned after that.
The steps on the day are covered in what full fibre installation involves.