This is some of the info I have learnt about BA booking classes, some areas are a little vague, but Economy has the most as it has the greatest price range.

First
Full Fare (F)
Restricted Fare with change fee (A)
Redemption or proactive upgrade (Z)


Club
Full Fare (J)
Semi Flexible (C, D)
Restricted with change fee ?? (R)
Inflexible / non refundable (I)
Redemption or proactive upgrade (U)

(J, C, D, I, R also appear on domestics too, not sure why, but they should all earn the higher tier points, only J shows as Business UK and gives lounge access)

Premium Economy
Full Fare (W)
Inflexible / Semi Flexible (not sure??) (E, T)
Redemption or proactive upgrade (P)


Economy
Full Fare (Y)
Restricted Fare with change fee (B, H)
Cheap economy (cannot be upgraded with Avios unless offered as airport upgrade) (F, K, L, M, N, O, Q, S, V)
Group booking (G) ???
Redemption (X, V; V is used when booked in via additional Gold availability or a double Avios purchase by a Gold)

(Y, B, H earn full tier points, the other classes get half tier points, redemption bookings get none)