A great way to have some fun
The TET has its own website -
https://transeurotrail.org/ - and there's a free app that can be downloaded which then allows you to download GPX files of the route to your chosen mapping app (Memory Map, Wikiloc, Google Earth, etc) for loads of countries across Europe.
The main underlying ethos of the TET seems to be to get people out into the scenic, rural areas using where possible trails or green-lane's. Which puzzles me slightly when you look at the route in Devon & Cornwall (which, Devon at least, has an abundance of green-lane's) as it seems to be predominantly tarmac based. It is understandable there has to be a trade-off between covering distance Vs the slower pace of green-lane's, but one wonders if whoever set the route initially wouldn't have been better off doing something like combining the Exeter & Lands End Trial routes as a base point. Still gives the opportunity for great adventure though
There is a facility to update routes, though I'm not sure how it works or what the criteria for amendment are?
It should also be borne in mind Dartmoor is the only place in the two counties you can legally wild camp, unless you seek the landowners permission before doing so.
For the UK, at least, you also need to check the legality of the route before setting off (TW2, definitive maps, etc) ...... We've followed large chunks of the route in Wales, and I know for sure that a couple of those lanes (Happy Valley & Strata Florida) have temporary closures on them at present
but has had supermoto wheels on all summer 
Forza 300 