>>>maybe i'm out of touch with the way Oyster works but can you buy a season ticket nowadays?
You can but season tickets but not in the paper form. You have to put them onto your Oystercard as credit. (Oystercards work in TWO ways. You have have season tickets, which are now called Travelcards, on them AND/OR you can have pay-as-you-go credit on them).
Ilford is in Zone 4. London Bridge is in Zone 1. Travel is by National Rail to Stratford and London Underground (Jubilee Line) to London Bridge. Fares are as follows:
Not using an Oystercard or contactless debit card: £5.80 each way
Using an Oystercard with pay-as-you-go credit or using a contactless debit card: £3.90 out in the morning peak. £2.80 to return home.
(Note that, as long as travel doesn't go outside zones 1 to 4 by rail, or anywhere in London by bus, the maximum that can be charged in a day (using either type of card) is £9.20. The maximum that can be charged per week using a contactless debit card (only) is £46.10).
Using an Oystercard with a 7 day Travelcard on it: £46.10 (but that includes unlimited travel within Zones 1 to 4 and on all buses, as well as work travel).
Using an Oystercard with a Monthly Travelcard on it: £177.10 (with the additional free travel mentioned above included).
Using an Oystercard with an Annual Travelcard on it: £1,844.00 (with the additional free travel mentioned above included).