It’s not really that difficult. The fairly standard dissolution clause used by Community Amateur Sports Clubs (CASC) will fit the bill:
In event of dissolution the proceeds after settlement of outstanding debts will go to either another CASC, the national governing body (ngb), a charity (with similar aims and objectives).
So, amalgamation is covered, central funds if you wish (Wing, Region, HQAC it’s up to you) the Air Scouts if you feel like being bolshie.
It’s non-public funds, raised by an external body and the Charity Commission would take a dim view of attempted interference. Most ngbs try to steer clubs towards donating it in that direction, but few take the hint.