PPL visiting the flight deck
I have my PPL completed, ATPL groundschool in progress, and I will soon be visiting my family in Australia so have several long-haul flights coming up (LHR-MEL). I'd like to see if I can visit the flight deck and have a chat to the pilots about their work, what they like, don't like, any tips... (I don't know many professional pilots, and definitely none in Europe, so I want to make the most of the opportunity!) I realise it might not be possible for security reasons but would like to ask anyway. My questions are: when and how?
I'm expecting that during boarding and the early part of the flight it would be quite busy so maybe I should wait until later, but then there are meal services, flight attendants get busy with other things?, ....
I'm also unsure whether I should ask one of the flight attendants to speak to the captain or whether I could write a note. The note would let me give some background but maybe a note would be unusual.
Anyone flying for an airline who can tell me what they would prefer? Or any other advice/suggestions?