I dont know about the Insignia, but I have done a few 1800 Astras now, but htese had noisy pulleys all the time, especially from cold, and ont was right throughout the rev range.

A good forte flushing, clean the solonoid filters, new pulleys (dont bother with just one), cam belt kit with new tensioner bolts. and Forte clean and protect with the fresh oil, and reduced interval oil changes in the future.