You should be able to select your entire assembly and rotate it to the correct orientation using the Steering Wheel. All the constraints would be preserved unless they referenced the base reference plane/coordinate system.
The simplest way to reorient an assembly - provoded all parts are constrained to the base part - is to re-orient the base or first part placed (this must have a Grounded relationship) using the Occurrence Properties command.
Right click on the first part in the assembly and select Occurrence Properties from the menu.
The Occurence Properties command will open allowing you to move the selected part in x,y,z and/or rotate it about the x,y,z axes.
Providing all other parts are constrained to the base part they will all move in unison taking up the new orientation.
Thank you for providing a solution.
But I have found a solution myself.
It's another way to....
The command I used for this = Move components
Did a rotate around a specified axis.
Anyway I'm glad I have a solution for this problem.