We went via fishguard, wales then Eurotunnel to France. Wales has some really lovely smooth country roads. Calais to Nurburg is a fair all drive but can be done in one day easy enough... We just bombed all the way down without stopping, it was middle of the summer in blistering heat, with A/C barely working so I dont have fond memories of that leg.

Keep in mind sometimes they might close the track due to accident and you might not get out at all that day. We spent two days there and were lucky enough to get out good few times. It definite aint cheap for a lap. I'd recommend getting an instructor to hop in with you to make the most as it is intimidating track.