The following gown was created by Doll Clothes of Yore.
The costume designer in the 2009 BBC version of Little Dorrit used beautiful costumes from the 1820s and 1830s period. During this period, the fashion was moving away from the plain, straight ancient Roman-inspired gowns, to Romantic "historicism" which had slashed sleeves and many embellishments, reminiscent of the medieval period. By the 1830s, the very fashionable gowns had puffy sleeves and bell shape skirts.
Here's a timeline of gown silhouettes, so you get a better idea of what I'm talking about.
These styles seem earlier than the ones above--probably 1820s.
Real examples from the 1820s:
Definitely 1830 gown...