Possible Clues:

• For a treat, motoring organisation rings school - it's a godsend
• On top of everything, a relative entertains graduate going back to America
• "On top of that ... "
• It's a stroke of luck for a school head, missing in West African country, contacting my group
• Thrown in, say
• It's a stroke of luck for a school head missing in West African country contacting America
• What a godsend for Roadwatch to cover safety first with an added feature
• Thrown in
• For a treat motoring organisation rings school ¿ it's a godsend
• For a treat because sailor is on from America