This is what the Church of England says:
You may have military standards, guidons and colours laid up in your church. They belong to the state and you cannot dispose of them without Ministry of Defence sanction and a faculty.
Once colours are laid up, they should stay where they are until they have completely disintegrated. Then, bury the remains with the staff and lion and crown colour pole mount in consecrated ground without any markings.
You are forbidden from replacing or conserving laid up standards, guidons and colours. Contact the Ministry of Defence for advice:https://www.churchofengland.org/more/church-resources/cathedral-and-church-buildings/flags-and-military-coloursStan
