The -300's were leased from Maersk, iirc, and were G-CMMP/R and G-BOZA/B - I last flew one of these on 25/1/1992
The -400's came into service in late 1991, I first flew one on 8/11/1991
The inherited BCal A320's were A320-100's G-BUSB/F, and A320-200's G-BUSG/K, all with CFM56 engines