The Open Space society can help your friends group apply for your green space to be a Village Green or Town Green (please see full details at our post as such registration is voluntary for council owned land).  They campaigns for people’s access rights too.

Their site is at: https://www.oss.org.uk/ In their own words:

The Open Spaces Society is Britain’s oldest national conservation body, founded in 1865.

• We campaign for stronger protection and opportunities for everyone to enjoy commons, greens and paths.
• We defend open spaces against loss and pressures from development.
• We assist local communities so that they can safeguard their green spaces for future generations to enjoy.

See also their page on Neighbourhood Planning and Protecting Open Spaces at: https://www.oss.org.uk/what-we-do/protecting-open-space/neighbourhood-planning-and-protecting-open-spaces/