Janneke Huitink’s dissertation (to be defended November 13 in Nijmegen) is now available on her homepage: Modals, Conditionals and Compositionality. Highly recommended!
[Disclosure: I am member of Janneke's "manuscriptcommissie" and also, as she says in her acknowledgements, "by far the most cited author in this dissertation" -- so I am surely a bit biased.]