Aegean Airlines Miles&Bonus - Same-day standby or changes on A3?

I hold an inexpensive revenue ticket LHR-ATH-JTR (fare classes S & Q, not sure about the booking code, maybe S2JA3C?) and am curious about whether it's possible to get onto an earlier flight out of London.

Does Aegean Airlines have any special standby or same-day confirmed change rules?

Looking at what I think are my fare rules I don't see any special provision for standby travel.

I do see language indicating that changes are permitted with a pretty low change fee (€30, £25, $50, or 8500 HUF, if ITA is decoding this correctly), but I'm not sure how that would work in practice since my ticket is owned by a travel agent who charges their own change fees to touch a ticket.

Normally by the day of travel, the airline "owns" the ticket, not the travel agency, although some carriers notoriously charge an additional fee to change any ticked that was not issued by them.

My only vaguely close experience was once missing a Greek island flight on Aegean in business class and being rebooked on a later flight with no fuss, no muss and no fees or additional fare charged. My wonderful travel agent took care of it instantly.

All A3 tickets can be changed for a fee (usually 15 Euro).