If you're using AP tickets, split at GLQ. AP SB is a tenner, plus the single to DBC. (Total: £20 + £6.80 -
£26.80 OR £34.20 + £6.80 =
£40). This of course deponds on availablity of the Advance tickets.
If not using AP, the SDS INV-DBC via Aviemore comes at £44.90 for an adult. (Total:
£89.80)
I would not recommend splitting at any other points as this does not seem to yield any better fares, although I am open to correction