£74 if you wish to travel with your Y-P before 10am, £39.80 afterwards.
Slight correction: The £74 ticket (well, £73.90 to be exact!) is valid after 0930. The £39.80 ticket was valid at any time under BR and in the early days of Virgin XC before they started ripping us off with huge fare rises.
Buying from Highbridge gets that down to £54.85 as the Off Peak from there is valid from 0500.
Assuming returning same day the usual splits are Birmingham (BHM), Derby (DBY), Sheffield (SHF) although some variation on that may be cheaper e.g. substituting SHF for Kiveton Park (KVP)
CNM - BHM SOR 18.80 (Valid any time)
BHM - DBY CDR 8.25 (Valid 0930-1529 and after 1815, but on weekdays before 10am you would pay 12.00 for this ticket)
DBY - KVP CDR 5.80 (this is the furthest toward Retford you can get for the same price as SHF)
KVP - RET SDR 4.60
The above is valid on the 0912 from CNM, they want you to pay £73.90 which is a rip-off but you can actually pay £37.45 which is the correct fare that individual people doing the individual journeys would be charged. The railway penalises people for doing a longer journey on some tickets, particularly if part of the journey takes place at what they consider "peak" time. This gives you a decent connection at Sheffield onto the 1144 to Retford.
If you do this on a weekend or don't mind getting to Retford an hour later, then you can replace the CNM - BHM SOR with a CDR, priced at £12.55.
