Goldilocks95 your advice is much appreciated (and I fully understand that it is informal!). In my experience so far having more than one bag is not an issue once you are through sefarcity. So on my last trip I had a shoulder bag squished into my carry-on, and my laptop under my arm (as they'd only ask me to take it out, if it was in the carry-on that didn't have room for it anyway). Once through sefarcity, the shoulder bag comes out, and the laptop goes in the shoulder bag, along with the sweater wrapped round my neck, and the various things I buy airside.