Hello I am a solicitor with over 15 years experience. I will try to help you with this.
Is this an existing drain which you wish to replace or is it an entirely new drain where none exists or has existed?
Do you have a legal right or easement to use the other's land for the purposes of drainage. Your solicitor should have made this clear at the time of purchase.
I am afraid that puts you in a very difficult position then. YOU have no right to put a sewer through your neighbour's land and ther ei sno reason why he can not agree to it subject to a fee. Can you continue to use your existing sewer?