Many thanks Brendan
I  think I didn't get 8d because I wanted the answer to be potagerie and I'm not particularly fond of the plants that are the answer.  It's taken me ages to see the hidden parsing for 17d.  I knew what the stakes were.  
I now just have one left 18ac for which I have ?I?I?G ?O?M.  But having just written it out horizantally I think I've got it - definition mess.  So obvious when you get them.  
I don't think I've got the right answer for 26ac, but I may not be up on "coups".
Thank you to Rossim for agreeing that this was a tough one.  It helps to know I wasn't alone in struggling.
Am I the only one who does the crossword on the paper?  Since we take the Guardian, I might as well use it.
I'm signing off now as I've some chores to finish before I can go to bed.
Thanks for all the help.