I use all of them in most circumstances... I'm not sure I'd say 'hi' or 'hiya' in a formal setting, that would be more 'hello' or 'good morning/afternoon' but certainly all friends/family/dept/collegues I'll say 'hi' or 'hiya' - and I'm not scouse lol, just always used 'hiya' which annoys me lol cos I hear myself say it in a really sing song kind of way and cringe lmao! I do think these days greetings are far more informal than they used to be - it used to be verging on a capital offence (slight exaggeration) to use the wrong greeting for the wrong person!
And Bug - EAT WOMAN! lol