Thank you for your email. I hope to be of assistance to you.
In my opinion, your neighbour in leaving ladders on your property constitutes a trespass to your property. Any person who enters your property without permission is a trespasser. If they leave behind any items then, if you do not permit those items to be on your property, that will also be a trespass.
You have a legal right to use reasonable force to remove a trespasser.
Therefore you may remove the ladders yourself. Do be aware though that you will be liable for any damage to the ladders whilst they are on your property and during removal. Therefore you could carefully move the ladders on to your neighbour's land (take care not to cause damage).
Why were the ladders there in the first place?
Have you received any reply from your neighbour?
Did the neighbour enter in order to carry out repairs to his property? You do not have to consent to this but the neighbour can get a court order to enter neighbouring land to carry out repairs to an existing building / structure (access to neighbouring land act).
I hope this answer is helpful. Please do not hesitate to contact me if you have any further questions or queries. I would be happy to assist further.
If my answer is helpful and you have no further questions please do not forget to accept /rate my reply otherwise I will not get paid for my time in responding and helping you.