It is more likely that the plate in question was attached to some type of ground radio equipment... probably a field telephone; as I have never seen one attached to any British WW2 aircraft. British airmen knew the phonetic alphabet by heart. A brief history (and variations) is as follows:
The Royal Flying Corps and Royal Army, standardized the terms in 1914;
A=Apple, B=Brother, C=Charlie, D=Dover, E=Eastern, F=Father, G=George, H=Harry, I=India, J=Jack, K=King, L=London, M=Mother, N=November, O=October, P=Peter, Q=Queen, R=Robert, S=Sugar, T=Thomas, U=Uncle, V=Victoria, W=Wednesday, X=Xmas, Y=Yellow.
There was another phonetic alphabet that concurrently and informally emerged within the RFC and Royal Army, commonly called "Signalese" or "Western Front Slang". It included many variations from the officially defined phonetics,
The Signalese phonetic alphabet was as follows:
A=Ack, B=Beer, C=Charlie, D=Don, E=Edward, F=Freddie, G=Gee, H=Harry, I=Ink, J=Johnnie, K=King, L=London, M=Emma, N=Nuts, O=Oranges, P=Pip, Q=Queen, R=Robert, S=Essex, T=Toc, U=Uncle, V=Vic, W=William, X=X-ray, Y=Yorker, Z=Zebra
The Royal Navy used the following :
A=Ack, B=Beer, C=Charlie, D=Don, E=Edward, F=Freddy, G=George, H=Harry, I=Ink, J=Johnnie, K=King, L=London, M=Monkey, N=Nuts, O=Orange, P=Pip, Q=Queen, R=Robert, S=Sugar, T=Toc, U=Uncle, V=Vic, W=William, X=X-ray, Y=Yorker, Z=Zebra
The Royal Air Force changed the codes during World War II, particularly with the arrival of the Americans in 1943.
1939-42 1942-43 1943-45
A Ace Apple Able
B Beer Beer Baker
C Charlie Charlie Charlie
D Don Dog Dog
E Edward Edward Easy
F Freddie Freddie Fox
G George George George
H Harry Harry How
I Ink In Item
J Johnnie Johnnie Jig
K King King King
L London Love Love
M Monkey Mother Mike
N Nuts Nuts Nab
O Orange Orange Oboe
P Pip Peter Peter
Q Queen Queen Queen
R Robert Robert Roger
S Sugar Sugar Sugar
T Toc Tommy Tare
U Uncle Uncle Uncle
V Vic Vic Victor
W William William William
X X-Ray X-Ray X-Ray
Y Yorker Yorker Yoke
Z Zebra Zebra Zebra
So; The plate would date from the early part of the War.