I saw my first (attempted) self-upgrader in the wild the other day. Husband and I boarded a short-haul flight to LHR. We were sitting in 1A&C. 1D&F were unoccupied when we boarded. As boarding progressed, a young guy slipped in to the space in front of seats 1D&F but didn't sit down, and motioned for people behind him to continue boarding. He continued to stand while being (unconvincingly) obsessed with his phone, only allowing himself the occasional furtive glance at the progression of people boarding. He couldn't have tried to look less conspicuous if he had stood with his hands in his pockets while whistling.

Boarding tapered off to a trickle of last-minute boarders, and our intrepid attempted self-upgrader began to take off his backpack, thinking his gamble had paid off. Just as he did so, an older couple boarded and quite directly said "These are our seats." Deflated, off he slunk behind the curtain.

Later in the flight, there was a rush for the CE toilets so the IFM suggested I go to the back as no one was waiting there. I spied the would-be upgrader sitting in 29F. Ironically enough, it was an empty row, so he ended up having a quasi-Club experience (with a 10g Graze bag and water, rather than a salad and drink). We were also a domestic flight assigned to gate A13 so we had to disembark from the rear door on to buses, so he even ended up as one of the first off.