When I am in my hammock I wear Chairman Mou fighting trousers. They were issued to me in the late 90s dont think they are on issue any more. Buffalo used to do fibre pile trousers they will keep you warm.
Wearing extra insulation does work but it's worth remembering that the compressed insulation won't be doing much if anything to keep you warm when between you and the hammock body. Clothing augments the top quilt very well but not much underneath: you'll still need a warm enough pad or underquilt
I just picked up a pair of these
http://www.ebay.co.uk/itm/HH-Helly-...583833?hash=item5b2ec36f19:g:5N0AAOSwiDFYLrYr