I have been through the Tree Preservation system trying to preserve a Fig tree in a public place but as it had not been listed in advance and no records could be obtained to protect that tree the Council brought in contractors in the early morning to cut it down.
You say that the trees are protected by an oprder each tree has its own preservation order and is numbered and the specis of tree noted, condition, height, gerth, proximity to buildings.
Any costs to appose and the loss of the cutting down, could only be made by the owners of the trees.
It is a sad fact that on requesting a meeting with the Tree peservation officer you will be imformed that that person is only a part time officer or is on holiday or not available, you will be delayed untill the trees have gone.
I wish you well but you cant beat the Council.