Hayo thanks for your response. Have been using iMac with PM 5 and seems to be working fine.
Something has also occurred to me regarding PM 5 and Catalina. I presume that Catalina will have security improvements in the same way that Windows does with updates. If I stick with PM5 but do not update to Catalina does this make my Mac more vulnerable? At present not keen on PM6 as it seems to be slow compared to PM5. I could update to Catalina and use Adobe Bridge with PS CC but this would entail a new workflow.
Your comments, and any other comments, would be appreciated.