I don't know the answer regarding foxglove seed and seedtape, Sarah. They self-seed so well in my yard, it is just a matter of moving the plants around to where I want them after they have had a season of growth.
I have made my own seedtape somewhat like the way you are doing it. Giving carrot seed a little something "extra" to help them get started is a
real good idea 
.
Carrot seed can take up to 3 weeks to emerge from the soil in my garden. Lots of things can happen to them :/ in that length of time. The soil surface drying out and the sprouts dying is the worse of it!
I wasn't sure if I was going to get a good stand of plants more often than 1 time out of every 3 or 4 years
. Then, I discovered pelletted seed and that really, really helped. But, pelleted seed isn't widely available
.
I came across some information from Colorado State University about using cornstarch gel to start seed. I used strips of paper towels to make a seedtape the first year but the 2nd time, I just "drizzled" a line of cooked cornstarch gel into a furrow and sprinkled the seed on it. This works just about as well as pelletted carrot seed! I couldn't have been happier
!
Apparently, the gel holds moisture against the seed while it takes all those days to germinate.
Steve
"To make a gel for planting seeds, add one tablespoon cornstarch to one cup of water and bring to a boil. Cool the starch mixture to room temperature . . ."
