Four private equity firms are finalising their final offers before the deadline on 20 January.
Two known bidders are Terra Firma and CCMP.
Insiders suggest the preferred bidder could be Terra Firma and that could be announced by the middle of next week. But other sources suggest the announcement of the sale, which could be for up to £300m, may not be made for several weeks or even months.
Neither the company nor HBOS bank, which controls GCG, has a preference as to who takes over. They will evaluate bids and associated terms and conditions after Friday.