So having spoke to the very helpful
@yorkie I have been encouraged to make a thread on the issue above so please feel free to add your opinions,experiences.
So for my issue I experienced today I was on an IET from Truro at 13:01 to (What was meant to be Penzance) Redruth so I sat in the 1st class area having double checked via trainsplit,GWR tickets that there was no avalible tickets to purchase for this area and RTT for the standard only part to make sure.
To cut a long story short I was removed by the TM after multiple backs and forths with evidence, stares from him of around 10-15 seconds (not exact) and claimes from him "RTT is nothing really' despite it saying standard only I get removed over "the timetable PDf is showing IET with 1st Class and this is what you have to follow" and just get out Redruth rather than carry on with it.
Is this correct? Even if you can't buy first class fares for these Exeter/Plymouth to Penzance, you have to go off the timetable? I'm not bothered about a bigger seat. I'm perfectly happy in standard it's more the constant wasted space on these services. I hope GWR will sort this out for a very simple capacity boost.