Lettuce appreciation society

In my photo of the GH, there's a bolting lettuce at the back right corner. I leave them to flower and form fluffy seedheads which will dry on the plant. If you cut them off then and put them in a bag/bucket, they'll fall off (with some gentle persuasion) and you get masses of seed from one plant.
I have some Morton's Secret Mix -might need to sow those in another GH. BTW, Real seeds have Red Iceberg seeds.