There is no Club Inter-Continental "floor" per se; the Lounge proper is on the Mezzanine floor (IIRC) and you gain access by, usually, paying the Club Inter-Continental supplement of about 500 - 700 HKD PRPN. There is a range as it seems the "rack" rate supplement is 700 HKD plus tax per room, but the hotel often offers it at a "discounted" 500 HKD plus tax.
I called the hotel directly to book my special package which was on their website -- 2400 HKD for Superior Harbourview room including Club floor access -- which I thought was a very good deal, considering my upgrade.
I believe you can book the Club floor through Inter-Continental telephone reservations; by calling the hotel direct; or e-mailing them. It is odd that you cannot book it on-line; I will take a look..... perhaps in the mean time someone else on this forum might have a simpler solution?
Best,