Thanks for those suggestions I will give them a try, and I will post my findings in the other thread. Save having two threads going at the same time.
I am using 25mm aluminium conduit but I am thinking aluminium is too soft for this purpose so may have to switch to galvanised or zinc coated steel. Also the conduit from our hardware store is apparently 25.4mm or 1″ rather than 25mm. I haven’t measured it but it was hard to push in and wouldn’t fit in any of the international edition parts without some tweaking and drilling. I guess the aluminium would have just been squashed under the pressure.