In law a private bailiff is required to make peaceful entry which can be by way of an open door or window even if they use a ladder, I am aware of a bailiff entering through an open Garage where there was an internal door, it must be peaceful, force must not be used. Once peaceful entry has been made a bailiff will prepare a walking possession order, which is a list of property owned only by the debtor, which they can seize and they will ask for the list to be signed. Once this is done force can be used to enter on a subsequent visit on the grounds that it is being used to repossess their property. Cars left outside can be taken, if the property of the debtor, and often are as they represent a reasonable amount of money and can cause major inconvenience.
Only the debtor’s items should be taken and anything used for work and fundamental items of cooking and living should not be removed.
In practice a private bailiff may assume you have no knowledge of the law, and may suggest they go inside, you do not want the neighbours to hear, I have the right to enter, I have a van to remove goods if you try to stop me entering, are all excuses I have heard, whatever they say do not let them enter.
If they gain peaceful entry they may list everything that will cause maximum inconvenience irrespective of ownership, which they will sort out afterwards.
Your protection is a basic knowledge of the law, if force is used to try to gain entry call the police; hot days when doors and windows may be left open are a favourite day for gaining peaceful entry.