Mike, you can use the global acars web site
http://www.acarsd.org/acarsquery.html
The registrations should be ..
ACARS mode: 1 Aircraft reg:
G-CIVE [Boeing B744]
Message label: ** Block id: @ Msg no: 39e4
Flight id:
BA0009 [LHR-BKK-SYD] [British Airways]
Message content:-
SBS-1 Callsign: BA9
----------------------------------------------------------[ 12/03/2009 23:03 ]-
ACARS mode: 1 Aircraft reg:
G-YMMP [Boeing B772]
Message label: ** Block id: @ Msg no: 3a02
Flight id:
BA0015 [LHR-SIN-SYD] [British Airways]
Message content:-
SBS-1 Callsign: BAW15
----------------------------------------------------------[ 12/03/2009 23:05 ]-