The real no-nos are double-sided pedals like SPDs, QRs and (obviously) gears and brakes. Tri-bars aren't allowed either, unless you're out on your own or pursuiting.
IME no-one checks BB height at Newport or Calshot, although they might moan if they think you're using the wrong gearing because it's slightly harder to do bunch exercises when one guy is on 48 x 16 and the rest are on 48 x 15.