I've given Alistair's vhs-teletext program a try on output from a Betamax tape tonight. Since Betamax is technically superior I was expecting to be able to see headers on the TV, but I can't; I might need a better tape as this one's a bit noisy.
It did manage to pick a single page out of all the mush - and what a page to pick:
Notice the page is 2FF. I wonder if this was some sort of padding or a terminator page for magazine 2?