Our GC here had all their seeds on the stands in January, and according to the lovely lady there, the Unwins Rep was pretty thorough at getting the Shirley toms in, which were forgotten last year!
I'm wondering if there are fewer seeds in many of the F1 packets, and maybe some of the flowers, although we don't grow many from seed, just veg etc...
I did learn that if the trial germinations of the seeds from the previous year don't reach around 95% success, they ditch the lot, but if I was a betting man, I'd say that seeds like cucumber are bred to die before they reach your greenhouse, and also courgettes have a suicide vest attached to them as well! They do here, so I buy plants and think of England!