Avoid the A30 at Bodmin at all costs! They're building the bypass (at bloody last! ).
It's chaos and will be worse by then. I'd go Plymouth and fork off at Dobwalls
Having done Exeter .to Falmouth and a few other up and down routes in the last week , i can't think of a good way in or out of Devon and Cornwall at present unless you are on a bike .
The Liskeard bypass has a contraflow with one side closed for half its length , that will caus a back up to the bridge
there are new roadworks at Bodmin where you join the A30 , they have put in a pedestrian crossing there for christ sake
Then there is the new by pass going through Gossmoor and on the other side the big roadworks at Oakhampton on the A30.
Not sure if the A38 is finished yet at Ashburton .
I can see the whole of the 2 counties with one jam from exeter to truro .
As for the caravans , oh I best not go there I have a soft spot for them , somewhere near where I ride my kTM