Hi Rob,
Thanks for your reply. It's very public spirited of you to take the trouble to alert X-Part to the thermostat problem. I did the same thing concerning the modified "drop links" which are inferior to the original design.
Your curved pipe and thermostat housing won't break so long as you remove the black manifold chamber and the LH bank inlet manifold for access, use lubricant on new 'O' rings and resist being heavy handed!
I'm afraid that I'm as puzzled as you are regarding your air con. I can't see how a re-gas will help.
Looking forward to the result of your bench test of the newly supplied thermostat.
Simon