phpexcel not maintaining charts in read/rewritten spreadsheet - phpexcel

Question

I'm trying to use PHPExcel to produce spreadsheets with charts based on "templates" that non-coders have created and formatted, but with data for the charts injected by my code. I've created a "template" spreadsheet including a chart which is looking at the appropriate data range, so I want to read it in, set cell values (which are the data range for the chart), then write it out again.
In the output that PHPExcel produces, the injection of the data has worked, but the chart is missing. It's Excel2007 (not guessing, i'm getting it to identify) and I'm doing a setIncludeCharts(true) on both the reader and the writer.
Any ideas? (other than getting PHPExcel to create the chart. I can't really do that because I need non programmers to be able to create the templates that my code just puts data into based on them providing the cell reference where the data insert should start).
Many Thanks
Code (that works other than charts disappearing in output):
// Identify the filetype (it returns 'Excel2007')
$filetype = PHPExcel_IOFactory::identify("template.xlsx");
// Create the reader and load the file
$objReader = PHPExcel_IOFactory::createReader($filetype);
$objReader->setIncludeCharts(true);
$objPHPExcel = $objReader->load("template.xlsx");
// Inject the data
$objPHPExcel->setActiveSheetIndex(1)->setCellValue('A3', 'Category 1');
$objPHPExcel->setActiveSheetIndex(1)->setCellValue('B3', '10');
$objPHPExcel->setActiveSheetIndex(1)->setCellValue('A4', 'Category 2');
$objPHPExcel->setActiveSheetIndex(1)->setCellValue('B4', '20');
$objPHPExcel->setActiveSheetIndex(1)->setCellValue('A5', 'Category 3');
$objPHPExcel->setActiveSheetIndex(1)->setCellValue('B5', '30');
// Output headers
header('Content-Type: application/vnd.ms-excel');
header('Content-Disposition: attachment;filename="' . time() . '.xlsx"');
header('Cache-Control: max-age=0');
// Prepare PCLZIP
define( 'PCLZIP_TEMPORARY_DIR', '/tmp/' );
PHPExcel_Settings::setZipClass(PHPExcel_Settings::PCLZIP);
// Create writer and spit file out to browser
$objWriter = PHPExcel_IOFactory::createWriter($objPHPExcel, $filetype);
$objWriter->setIncludeCharts(true);
$objWriter->save('php://output');