I finally managed to resolve the issue, there were a couple of problems in then end. It was all due to the way I was trying to remove the item from the array or arrays. The code I should have used was this:
AppDelegate *delegate = [[UIApplication sharedApplication]delegate];
[[delegate.packing.packingListArray objectAtIndex:indexPath.section] removeObjectAtIndex:indexPath.row];
I then had an issue with the way I had my arrays defined as they were built from a plist which although set as NSMutableArray they were being converted to NSArray. So at the end of that statement I included.
........mutablecopy];
All problems resolved :)