A few guys I know have struggled getting an interview date sorted. From what I gather it’s just a case of patiently waiting for slots to open up and keep checking. Frustrating I know.
As for what fleet you might get offered.....being Bus rated doesn’t necessarily mean they’ll use that but would imagine they’ll try to if poss. As I said above, a guy I know is A330/A350 currently and has a start date on the 777. A350 DEP’s are probably a way off yet judging by the internal comms but never say never.
You could literally be offered anything but wouldn’t expect BA to start you on something and then switch you to the 320 on day one. As I said, never say never.
Best of luck with it.