Thanks Mike,
I must admit I hadn’t even thought about the Slade Green to Abbey Wood end. If I held a weekly Z1-4 travelcard or had reached the Z1-4 weekly cap, I would probably use the bus rather than the train. There’s really not much in it in terms of door-to-Abbey Wood journey time. My habit of traveling from Slade Green on a Saturday was only formed because I normally buy a Z1-6 day travelcard.
I agree with you entirely that fares should be predictable.
Phil