Zaxis,
I had exactly the same experience when I visited Ashburton two years ago. A lovely museum with, as you say, friendly staff.
I had a really big surprise when I came face to face with a Harrier! I had never seen one up close and I hadn't realized how big it was.
If you haven't already done so, don't miss the RNZAF museum at Wigram (Harvard on a pole as you drive south out of Christchurch). If you are "up north", MOTAT in Auckland and Classic Flyers in Tauranga are "must sees" if you are near by.