I forgot to update this thread, and thought a couple of points might be useful to anyone else with a lengthy stopover in HKG.
Being a Gold Marriott member, the hotel provided a courtesy car to the hotel, which meant no taxi required. Just email the hotel in advance, and they'll do the necessary.
The hotel is only a 5 minute drive from the airport, and is a typical modern Marriott. My room was nice, although in reality I just walked in, shut the curtains, and slept for 6 hours! Woke up, grabbed a shower, and headed back to the airport for my second leg flight to SYD. The hotel was reasonably priced, and made a huge difference to my travel day. I got on the second flight refreshed, rather than shattered, and was in good shape when I arrived in SYD. I'll definitely do this again on my next trip there.