Yesterday (26/04/19) was only the last day of timetabled S Sets on the main line.
There are only 13 S Sets left: S2, S56, S61, S64, S65, S97, S99, S100, S103, S113, S135, S140 and S145.
Recently Withdrawn sets are: S28, S67, S69, S104 and S123 (All containing heritage cars except S69)
S103 may be next as it does not have a proper target plate like S67 because they know it won’t be around for long. S100 might still remain for a while as it got brand new target plates about a month ago.
If they are to take the heritage carriages from the withdrawn sets and create new sets, possible sets could be:
S101 - C3765-T4926-T4002-C3912
S102 - C3021-T4101-T4018-C3748
They may number these after S100 (S100-S105(If 6-4 Car Sets)/S111(If 6-8Car Sets)because they would already have the target plates for most of them.