Eight minutes in (plus 10 minutes for completing the registration questions):

"This is not the survey for you"

There were so many questions along the way that I don't have an idea what the poison pill was. I think I hit the wall when I said I don't know anyone with COPD, dementia, eclampsia etc. Alas. I was offered a chance at the prize and another survey that started with that question.

ETA: Four surveys in, so far. Current blockage is this:

"Using the scale below, please show how well informed you feel about managing your own investments"

...but no scale appears. No way through or around it - back, reload, rinse, repeat, relaaaax etc. Alas. But the good news - possibly for this thread - is every time I am bounced, the new offer is for 600 Avios as if I'm a virgin.