If your route uses rights of way on land owned by local authorities or by private landowners you don’t need their permission but it is polite and sensible to contact them. If it uses roads, then you should contact the relevant local authority’s highways team. You may also have to approach other departments of the same or another tier of local authority to consult them about the location of checkpoints and event facilities. Local authorities are structured very differently in different places. It’s wise to make the initial contact by phone to find out which authorities you need.