I'm looking to find the best deal here with split ticketing if necessary?
Travel time is 09:29
Hmm. Can of worms anyone?
A Sevenoaks to London St Pancras Off Peak Day Single (CDR) has validity code C4, "by any
train scheduled to arrive London Terminals
or Kensington Olympia at or after 1000" although you arrive at St Pancras after 1000, the 0929 is considered a "peak" train for this ticket, as the restriction is based on when the train is due to arrive. In this case, as you change at London Bridge before 1000, it is considered "peak" therefore not valid, by the booking engines.
However note that if your ticket was to London Terminals and your destination was Charing Cross, then as this train arrives after 1000, then it is valid!
This train may, or may not, be valid on a specific Off Peak (Day) Single/Return ticket depending on various factors such as the origin, destination, and ticket type. There is no "peak on SE" rule as such! For each specific ticket, the restriction code must be looked up.
but by the time I reach Orpington it's Off Peak inside TFL.
Sorry to be pedantic but this isn't the best way to word it, as it doesn't quite work like that. I think you are trying to say that an Orpington to London Off Peak ticket is valid on that train? In which case, yes, that is true. But there is no such
paper ticket so Oyster PAYG would need to be used to benefit from the off peak fare from Orpington.
My preferred route is not via LU but on Thameslink. A single ticket for this seems to be £11. It seems around 40-50% cheaper to buy a peak single to Orpington and then use Oyster PAYG off peak but that would mean having to get off my train, exit, tap in and wait for another train to London Bridge - acceptable but not ideal.
Sorry to be pedantic but the ticket is Anytime Day Single rather than peak single. In this case, we know what you mean though so it's not a problem
I'm not entirely sure that an Off Peak Day Single to St Pancras is not valid on the 0929. There is an argument to say that you are on a train that is scheduled to terminate at a London Terminal after 1000, therefore it is valid. The booking engines say it's not valid because they do not realise this fact.