The Johnster said "My knowledge of the Cockney alphabet is incomplete, and perhaps someone here can fill in the gaps for me".
The version I learnt many years ago is a bit different but fills many of the Johnster's gaps
A for 'orses (hay for horses)
B for mutton (beef or mutton)
C for 'th highlanders (Seaforth Highlanders)
D for 'ential (deferential)
E for brick (heave a brick)
F for 'vescence (effervescence)
G for police (chief of police)
H for respect (age for respect)
I for Novello (Ivor Novello)
J for oranges (Jaffa oranges)
K for restaurant (kaff or restaurant)
L for leather (Hell for leather)
M for 'sis (emphasis)
N for 'a dig (infra dig.)
O for the wings of a dove
P for relief
Q for a song (or a bus)
R for mo' (half a mo')
S for you (it's for you)
T for two (tea for two)
U for mism (euphemism)
V for Espania (viva Espania)
W for quits (double you or quits)
X for breakfast (eggs for breakfast)
Y for Gawd's sake (why, for God's sake?)
Z for breezes (zephyr breezes)