APD has nothing to do with rail travel, so your train tickets would not make any difference. Furthermore, the APD will be chargeable unless:
- Each [ticket] refers to the other and states that they are to be read in conjunction
- There is a summary of the flights constituting the passengers journey including the flights in question
- Although the flights may meet all the other criteria for determining whether 2 flights are connected, they will only qualify for the exemption if the connection is evidenced on the ticket or a flight summary.
If you're flying, you
may get the airline currently assessing APD to update their systems to note the other flight and thereby allow APD to be waived, but actual experience with this is mixed. In general, there's no obligation for airlines to create references to other tickets for the purposes of waiving APD–if you buy the ticket from a TA on two different airlines and they sell them together that's one thing, but if you buy two totally separate tickets then you're at the mercy of the airline.