Forgive me if this has been discussed before, but a friend and I were just discussing Marion's final payphone call to Sally on 31 July, which she said was form Tunbridge Wells, England. I know there are theories that she may have been calling from somewhere else on her way back to Australia, not from the UK, and I believe Sally only had Marion's word that she was calling from Tunbridge Wells.
How Sally describes the call does support the theory that Marion was not calling from a UK payphone. She says Marion had to redial a few times because the money kept running out. That is a red flag to us UK sleuths because with a UK payphone, whether you were using a pre-paid card or cash, the call would not just cut off when the money or credit ran out, forcing you to redial. You had a warning signal: if more money or a fresh pre-paid card was needed there was a series of "rapid pips" that both parties could hear. You had maybe 10 seconds to fumble for change or a new card, and only after that would it cut off if you didn't take action. I found a recording of the "rapid pips" here and I have passed them on to Joni:
https://www.pond5.com/sound-effects/item/8634028-bt-dial-payphone-pips
The "rapid pips" are very familiar and nostalgic to anyone who remembers the UK before mobile phones eclipsed payphones. They were very intrusive to the conversation. We all used to ring our friends and family at home or overseas from payphones and the pips would drive us nuts.
Separately, Marion's remark to Sally that she was in Tunbridge Wells "having tea and scones with some little old ladies" has always seemed a little bogus to me, like she was making it up. Apart from sounding made up, the call was made in the early morning UK time, and you wouldn't have tea and scones at that time. I know it sounds ridiculous, but they are just not breakfast food. "Little old ladies" and Australian tourists like Marion who wanted to act all British and dainty would have them in the afternoon at a tea shop or hotel lobby, not at dawn.
While I don't want to paint Marion as a deceptive person, it seems to be generally accepted that it was she who returned to Australia barely a day after this call. If it was her, she lied by omission to Sally about this imminent trip home to Australia *that same day*. Perhaps as the landing card says, it really was meant to be a quick one week trip home to sort out something that had arisen during the trip to Europe, and Marion preferred not to disclose it to Sally. After all, we do know that Marion had seen fit to not be open in general about aspects of her new relationship and her planned trip. That, plus the half-truths on the outgoing passenger card, do possibly suggest the influence of someone to whom deception is just their daily life.