they looked pretty good but the modules looked s if they were only about 1.5 inches.
I never saw the programme, and for that matter I never watch GW
In terms of modules the ones you describe sound a bit like what I use as seen here:
or these subject to the size of seedlings I am pricking out.
To get a better idea of size these are insert trays I put into a standard 14" x 8" tray.
It is all a question of timing how long your plants are going to be growing on until planting out time.
More often or not I use the 24 cell tray for my bedding.
If I am growing largish plants I would use a 7cm pot :
In the case of Cosmos I would probably use the 24 cell tray but having said that I would use a 7cm pot for plants such as Dahlias (Both of these eventually grow into similar sized plants) so in my opinion it would be: either / or!