That`d be like the label on the titanic thendamorad said:Just moved the non-return valve to mains side and used an isolating valve to bridge the connection between the flexihose from expansion tank and heating system.
Thanks for the help. I appreciate the advice I have been given by you all...
PS I know I shouldn't have anything between the expansion tank and the system but I will label it "LEAVE OPEN except whilst carrying out maintenance on the expansion tank."
I promise...
Thanks again...