Obviously these ones are for BA.

The offical guideline booking class codes are:

A First Class Discounted
B Economy/Coach Discounted
C Business Class
D Business Class Discounted
E Shuttle Service (No reservation allowed)
or Economy/Coach Discounted
F First Class
G Conditional Reservation
H Economy/Coach Discounted
J Business Class Premium
K Economy/Coach Discounted
L Economy/Coach Discounted
M Economy/Coach Discounted
N Economy/Coach Discounted
P First Class Premium
Q Economy/Coach Discounted
R Supersonic
S Economy/Coach
T Economy/Coach Discounted
U Shuttle Service (No res. needed/Seat guaranteed)
V Economy/Coach Discounted
W Economy/Coach Premium
Y Economy/Coach
Z Business Class Discounted

For example both Virgin and BA use W Class for their Premium Economy Products (WT+ in BA's case); however discounted Premium is K Class on Virgin but T Class on BA.

This information is from http://www.airodyssey.net/reference/othcodes.html

Take a look at the site itself, http://www.airodyssey.net as it contains lots of useful informatiom on codes, aircrafts and has a good multimedia library too.

Thanks,
Richard