The officials for 99% of American Football games played in Britain are all members of BAFRA, the British American Football Referees' Association.
BAFRA was founded in 1984 to provide officials for the then fledgling sport. In the early days the majority of its members were US military personnel stationed in the UK but now the membership is almost entirely British.
The Association's aims are five-fold:
BAFRA covers several hundred games at all levels, including Senior (over 18), College, Junior and Youth games. Through the International Federation of American Football (IFAF), BAFRA also provides officials for tournaments on the continent.
BAFRA's pack of information
for teams is available
See it here.