These rear access ways were installed to allow the delivery of coal to a house without it having to go through the house and to allow dustbins to be taken out the front again avoiding going through the terraced houses.
Do any of the neighbours still use the passage for this purpose or similar purposes?
The neighbours have effectively closed the easement by extending their gardens. It is also arguable that the point of the easement , the delivery of coal to coal sheds in the gardens etc has ceased to have any effect due the passage of time.,
I would put gates up and lock them, any neighbour who objects can explain why they have blocked the right of way themselves and , at least, you had the sense to make the back route available in an emergency.
The right of way will still exist on the deeds it has simply become ineffective as a result of the passage of time. This is not unusual many strange laws have never been repealed but are simply not enforced or effective.
No neighbour should have left anything in the passage way. It was a passageway with a right to pass. It cannot be blocked , impeded or stuff left there so I would give them their fence back.