If you do end up getting the train, our Biker Chick had to arrive minus bike last year so, with rucksack in hand, she got the TGV from Brussels and then the new tram from the mainline station to the end of the line, meaning that I collected her effectively from right by Houx Annexe, rather than heading all the way into town. Campsite pass not needed, as they are per vehicle, she stayed on our pitch and we dropped her back at the tram post-race on out way out. Buy the GE ticket on the gate. Easy peasy.
MG Mark