Looking at possible itineries, clearly we will spend some time around Siem Reap, Angkor Thom, Angkor Wat temples, Ta Prohm, Kompong Khleang.
Then Sihanoukville, Kep, Kampot.
Then Phnom Penh and Royal Palace
Then some places around the Mekong - Kristie Island Koh Trong, Sen Monorom

We will have already been to Myanmar and Laos, so will have seen lots of temples and done a river trip.
Any recommendations on split of time above or other places to go?
Thank you

I'd include Siem Reap [4 nights], but if you've just spent days tramping round the temples at Bagan you might not want to do the same at Angkor.

A daytime bus to Phnom Penh will take 6 hours, a one hour flight will eat up probably 5 hours with getting to the airport, checking in, hanging around, getting from PP airport to your hotel. Personally I'd opt for the bus and use Giant Ibis...

http://giantibis.com/

3 nights in PP. A great full day is hiring a tuk tuk for about US$20, and visit the Killing Fields, which despite the atrocities is very tastefully presented, and the admission includes an audio guide, which as soon as you put it on will be totally immersed for the next 90 minutes or so. Then move on to Tuol Sleng Genocide Museum, which in contrast to the Killing Fields is a raw experience. Then have lunch before visiting the Russian Market. Finally back to your accommodation, pay off your tuk tuk driver, then relax for a couple of hours before going to the Foreign Correspondents Club on Sisowath Quay for their Happy Hour [1700-1900], arrive a few minutes early and get a seat on the balcony overlooking the traffic madness down on the Quay. It's a memorable day out, the Cambodian people really want visitors to see what they had to endure during the Pol Pot era.

Bus or train to Kampot for 3 nights, make sure you hire a tuk tuk for the day to visit Kep and include a pepper farm along the way. Have lunch in Kep by the sea.

You could also include Battambang, beautiful countryside, and a ride on the Bamboo Train.

Thank you, but important as it is, I am not sure I want to see stuff about the Kiling Fields. I saw a TV documentary and know that is is very grim.

This is some other input I had.
The sights in Laos are very spread out, and internal travel is not rapid. So you might want to stay in the centre of the country. You could spend a day or two in Vientiane, plus a day trip to Nong Khai, which is a pleasant little town just across the Mekong in Thailand, which has some agreeable riverside walks. There are two tourist spots between Vientiane and Luang Prabang - either Vang Vieng, which is an outdoor adventure centre, or Phonsavan, which is near the 'mysterious' Plain of Jars - a giant archaeological site. All that, plus the necessary bus journeys could take you to Luang by 24 December. Luang is worth a couple of days, plus there are a couple of day trip sites nearby - ancient temples, caves etc.

Sorry, ignore comments on Laos, I put it in the wrong post!

Funny you should say that about the Killing Fields, the first time we went to Phnom Penh we had exactly the same thoughts as you and never went there. But I regretted that decision, and made sure we went there on our second trip. Like I said Killing Fields is tastefully presented, but the Genocide Museum is raw.

What you'll see in Cambodia, and particularly in Phnom Penh are a fair few locals who've lost limbs as a result of Pol Pot, or since the end of the conflict have been unfortunate enough to stand on a land mine. So if seeing a documentary about the Killing Fields was grim, then seeing some of these unfortunate folk in the flesh won't be very easy on the eye either.

Me again!

Here are reviews off Trip Advisor from visitors to the Killing Fields...

https://www.tripadvisor.co.uk/Attrac...hnom_Penh.html

All part of Cambodian living history. But if the reviews don't help change your mind, then fair enough.

I mentioned above about finishing at least one day by going to the Happy Hour at the Foreign Correspondents Club...

https://fcccambodia.com/fcc-hotel-phnom-penh/

On the Home page is a photo of the FCC from Sisowath Quay. Grab a seat one of the balconies

I really like Phnom Penh, plenty to see and do. Of course you don't have to go to the killing fields but far from being grim, I found it to be a very peaceful and reflective sort of place. Tuol sleng, on the othe hand was one of the most chilling places I have ever been to.

As Lancaster lad suggests , engaging a tuk tuk driverto take you around for a few days isa great way to see the city

Kampot and Kep are lovely and would be good for a few days and there is now a train from PP to Kampot which would be a fun way to go. Rikitikitavi is a nice place to stay - terrific food!

Battambang has a lot to see in the surrounding area, bamboo railway, bat caves, lost of temples and makes a good mid way stop between PP and SR.

Some info and photos from our time there last year on our blog @ https://accidentalnomads.com/category/cambodia/

We initially started with a reservation for 6 nights (we'd just arrived from the US and knew we would need some recovery time from jetlag) in Siem Reap. We soon discovered that we were much more into the temple ruins than we ever would have thought, so we added on an extra four nights. We were there in January, and it was so hot that we learned all of our touring had to be done either early (say before noon or 1:00) or starting in the later afternoon. The heat just wiped us out. Honestly, Angkor Wat itself was kind of a letdown due to the absolute hordes of people. WE much preferred other temple sites. We hired a driver and did an overnight to a Preah Vihear a remote temple on the Thai border (highly recommended).

We enjoyed our time in Phnom Penh much more than we would have anticipated. We did not go out to the killing fields themselves but visited the in-town genocide museum--sobering and depressing but critical learning what went on in the country. Highly recommended.

Kampot was a fun and different and very low key way to spend three or four nights. We'd definitely return here. On the other hand, our three nights in Battambang were okay, but it definitely the one place I'd cut if short of time. Hope this helps.