Me too. I just booked it with Avios. I won't have access to the MH lounge, unless someone with access lets me be their guest. There is a priority pass lounge I can use though.

I booked the Mary Beach Hotel and Resort in Sihanoukville. It is right next to the Tamu hotel, but quite a bit cheaper. I may change this depending on what others are doing.

I'm probably going to spend a couple of days in Phnom Penh after the Post DO. Siem Reap will be fun for those going there, but I've been there recently and don't want to go back so soon.