jethro's fleet listings says that they have ten aircraft:
GBXAR BAe RJ100 E3289 Union Flag
GBXAS BAe RJ100 E3301 Union Flag
GBZAT BAe RJ100 E3320 Union Flag
GBZAU BAe RJ100 E3229 Union Flag
GBZAV BAe RJ100 E3331 Union Flag
GBZAW BAe RJ100 E3354 Union Flag
GBZAX BAe RJ100 E3356 Union Flag
GBZAY BAe RJ100 E3368 Union Flag
GBZAZ BAe RJ100 E3369 Union Flag
GCFAA BAe RJ100 E3373 Union Flag