Hi guys!
I figured it out and it was a lot simpler than what I thought it would be 
I removed the filter on the chart and created a new variable
=[Average Turnaround (Minutes)] Where ([Contract Source] InList("SourceY")) where SourceY has been renamed but relates to the product
I have to amend the average line now! 
=Interpolation(Round(Sum([Paid Out Turnaround Time (Minutes)])/Count([Contract Number];All);0)) will bring the average for the whole report . .and when I use the Where clause to apply the contract source it isn't bringing the desired results 
=Interpolation(Round(Sum([Paid Out Turnaround Time (Minutes)])/Count([Contract Number];All);0) In ([Contract Source])) brought the correct result but this worked when I applied the filter to the chart but this now brings in the average for the Source X
I will appreciate further help where possible!
