West Kent to South cornwall

[TheImminentGin]

I expect this has been done to death but I have searched and not found it.
So I'm doing a Friday change over near Lostwithiel. Any route tips, leaving times, stopping places etc.

It is a long way for one day drive, and ideally break half way. I would think M3, then A303, A30 to Exeter. Then A38, but that's where it gets busy, through Devon and Cornwall.

Can't you ask AA or RAC?