If the wayleave is voluntary and there is provision to terminate this agreement and serve notice for them to remove the over sailing equipment, why don't you just serve notice?
If they then apply for a compulsory deed etc, they will have to compensate you for loss of value of your property and pay your reasonable fees I would have thought.
@Ferdinand is wholly correct in my view. The professionals including your lawyer when you bought the property, and architect should have identified the obstructions and advised you accordingly.
I had a similar situation with powergen a few years ago on a site, There was an easement for overhead lines 33kv if I remember correctly. Usually they have you over a barrel and you have to pay the costs of diverting them. But on this occasion the legal agreement had a lift and shift clause, where on notice, they had 3 months to remove them from the site. Straight away Powergen advised us that it would cost us £250k and take 12 months, until I produced the legal agreement. They said it was impossible due to their network agreements etc to divert them in 3 months. I just pointed them to the agreement and advised them to begin working up a compensation package for our losses. They started treating us with a little more respect then.