try
http://en.wikipedia.org/wiki/British_car_numbe r_plates#Current_system
or if too difficult
First letter Region DVLA Office Office Identifier (second letter)
A Anglia Peterborough A B C D E F G H J K L M N
Norwich O P R S T U
Ipswich V W X Y
B Birmingham Birmingham A - Y
C Cymru Cardiff A B C D E F G H J K L M N O
Swansea P R S T U V
Bangor W X Y
D Deeside to Shrewsbury Chester A B C D E F G H J K
Shrewsbury L M N O P R S T U V W X Y
E Essex Chelmsford A - Y
F Forest & Fens Nottingham A B C D E F G H J K L M N P
Lincoln R S T V W X Y
G Garden of England Maidstone A B C D E F G H J K L M N O
Brighton P R S T U V W X Y
H Hampshire & Dorset Bournemouth A B C D E F G H J
Portsmouth K L M N O P R S T U V X Y
W (for Isle of Wight residents only)
K Kettering Luton A B C D E F G H J K L
Northampton M N O P R S T U V W X Y
L London Wimbledon A B C D E F G H J
Stanmore K L M N O P R S T
Sidcup U V W X Y
M Manchester & Merseyside Manchester A - Y (MN reserved for Isle of Man)
N North Newcastle A B C D E G H J K L M N O
Stockton P R S T U V W X Y
O Oxford Oxford A - Y
P Preston Preston A B C D E F G H J K L M N O P R S T
Carlisle U V W X Y
R Reading Reading A - Y
S Scotland Glasgow A B C D E F G H J
Edinburgh K L M N O
Dundee P R S T
Aberdeen U V W
Inverness X Y
T Scotland (additional allocation) Glasgow A B C D E F G H J
Edinburgh K L M N O
Dundee P R S T
Aberdeen U V W
Inverness X Y
V Severn Valley Worcester A - Y
W West of England Exeter A B C D E F G H J
Truro K L
Bristol M N O P R S T U V W