I don’t think any of the tracks are sole use for bikes, if someone wants to walk up them they can and are entirely within there rights, same with dog walking/horse riding etc.
You may want them to be sole use, but that doesn’t mean they are.
http://www.forestry.gov.uk/nwepermissions
Your Right To Roam
The majority of our forests are dedicated as open access under Countryside & Rights of Way Act 2000 (CRoW) which gives walkers the right to roam across these areas. In many of the rest we operate a permissive right to roam policy. In addition we extend a permissive right to roam to cyclists and horse riders who may use our forest roads and tracks.
You can find out whether your event includes Forestry Commission land by using the MAGIC website.
Whilst everyone has right to individual and family recreation on open access land this right does not extend to holding events or running commercial activities.