New traveller on Virgin Atlantic

Hi everyone I am very new to this forum and also new to flying Virgin Atlantic. My husband and daughter and I are flying PE from Sydney to LHR (VS 201) in May and as I have never flown Virgin before I am unsure of what to expect on this long haul flight. Any hints or suggestions would be great. I have so much I want to ask but will start with food - are we able to take our own snacks/food on the flight as I am a fussy eater?? Also where do I buy my duty free alcohol and cigarettes as I read somewhere that I can't take them out of HK on the flight.... do I get these in arrivals at LHR?? Thanks