The place of theory?

I've got some helpful contacts on Twitter: this weekend some of them
have (quite rightly) pointed out that if I'm interested in using
grounded theory as a methodological approach, I shouldn't really be
setting out a series of propositions. Of course, in grounded theory
comes from the data as it is built and drawn upon to analyse 'what
bubbles up'. It's a good reminder to not get too wrapped up in the
detail of theory at this stage.

The funny thing is, I've realised the postgraduate research proposal
paperwork requires a certain amount of reference to theory, possibly
one if the reasons I've worked on this a little. Not having undertaken
a large scale research project using grounded theory to date, I wonder
if it's useful to have an idea of potentially applicable theory held
'to one side' - we all know researchers are not fully objective - BUT
to draw on this as the coding leads? Early questions, I know, but a
useful prompt from my friends who Tweet!