The last time I fitted T&G cladding, IIRC the batten spacing was around 24" and I used the little clips to secure it which resulted in no visible nails apart for the last piece which I covered using a bit of quadrant.
On this job I screwed the frame to the wall and the exposed beam (slanting roof, levelled off with cladding to cover joist) However when I put in the new ceiling in the spare room, it was a case of loads of pilot holes through the exsiting ceiling until I found the correct spacing for the existing joists. Bastard things worked out to be 14"
TBF it didn't matter what the old ceiling looked like as it was getting overboarded.
Info here - http://www.wickes.co.uk/content/ebiz...ages/gil/9.pdf
Clips - Wickes *–*Cladding Clips