Andy, I'm not familiar with a staghorn sundew but VFTs and S. flava can
tolerate fairly cold temparatures. Mine are in my back yard right now and
last night's temps went to about 15F or -9C. This is certainly not the
limit of their range. You might be best off keeping them outside. If you
think it might get too cold for them, bringing them inside an unheated
garage or shed for the winter might do the trick. Also, they need to be
kept damp but not dry or sopping wet.
Others can give you better tips on "artificial" (i.e. indoor) dormancy.
Hope this helps
Phil
PS - If you haven't seen it yet, check out the CP FAQ -
http://www.indirect.com/www/bazza/cps/faq/faq.html