When do I plant holly hock seeds? In the spring or the fall?
Answers:
Hollyhocks are biennial. You can plant the seed either in the spring or fall but late summer or early fall is probably best, since that is when they produce seed. Planting then will mean that the plants will flower the next year. If you plant in the spring, they would flower in the following year. They are quite hardy and certainly survive British winters regularly.
I just checked the Zone maps. Britain appears to be Zone 8 (which surprised me - I was expecting us to be closer to Michigan, or Zone 5, but our winters are not generally so cold, it seems). It would be worth trying to sow both in the fall and the early spring under glass.
This is a British website, but the instructions are pretty universal, of course: How do you steal your neighbor's roses?