Typically, I aim to leave the lounge at 30 mins before take off, putting me at the gate with 20+ mins to go. The gate screening is annoying, but they are not going to leave with passengers still waiting. At 20+ mins the crowd has gone down.
if in the premium cabins, I recommend the QR lounge. At the time of the BA flight transfers it is quiet. No stress on a shower and food and drinks, if you wish come very quickly. Otherwise the regular QF lounge is usually good for a shower as they have quiet a number so the wait is rarely long.
if OWE in Y or WTP then the QF first lounge is good. I am not a fan of it, but it dies it’s purpose. Dishes out lots of food in a cafeteria setting quickly.
KF