In message , Sacha
writes
This is a bit of a daft question but does anyone know if Tricyrtis come in a
larger flowered form than the T. formosana?

You could try enquiring of the national collection holder

http://www.nccpg.com/gloucestershire/tricyrtis.html

I suspect that there are larger flowered forms, but couldn't find
anything on a cursory search, if only because people don't bother to
specify flower sizes.
--
Stewart Robert Hinsley