It's unlikely they're going to dig and install new duct if the current duct can get the fibre drop cable underneath the wall and into your garden to then be clipped along a wall.

If you want the whole length done in new duct you'll probably have to buy it and install it yourself, and intercept the existing duct that surfaces by the wall.

You don't. Just order an FTTP service from an ISP and let the process play out.

Openreach will do what is required to get the connection operational.

In reply to a post by jpm:

It's unlikely they're going to dig and install new duct if the current duct can get the fibre drop cable underneath the wall and into your garden to then be clipped along a wall.

If you want the whole length done in new duct you'll probably have to buy it and install it yourself, and intercept the existing duct that surfaces by the wall.

I know for a fact that, that duct will be impossible to reuse as its congested and very old. Old enough to disintegrate from anything being inserted into it.

As Pheasant says: the process is that you place an order with your ISP, and when the installer turns up, they will discuss the options with you. The fact that it's marked "UG congested" means that you might get a surveyor turn up prior to the actual installer (which is good). You can then come up with an acceptable plan.