Ex BT here too. BT will only correct a fault for free up to where the drop wire comes in contact with your property, i..e. where the wire coming from the pole touches the side of your house. After that point it is your responsibility, so by the same logic, you may do as you wish to it and get anyone you want to work on it. I would not advise paying BT their £125 plus vat callout fee plus half-hourly charge to do it.
Source: ex BT 'apprentice', have worked on engineering, faults and customer service. Don't ask.