Hi Scott. You've mentioned two places that are jammed out at the times you mention.

Esperance is a very pretty town. There are a number of National Parks there but you cant pre-book them and they get jam backed over the summer and especially school holidays. Lucky Bay in Arid National Park is about an hour from Esp. but the RVs are packed so close together that if one person coughs at night, the nearby residents will wake up. Likewise all the CPs are full and you may find that they are already booked for this Xmas. Try the Pink Lakes CP - the cheapest in town and with an IGA and good all ladies butcher across the road. Good facilities. Esperance shire bans free camping and apparently their Rangers are always on the lookout for "offenders"

Anywhere at Xmas in SW WA (from Esperance right round the coast and up to Mandurah) fills up during school holidays.

Suggest you start finding out the various CPs in those areas and emailing them to see if they have any sites free. There are a lot of free or low cost RV and tent areas on the SW, but again you will struggle to find a place, especially in January as many of those from Perth will head south when school hols finish and stay in the area until the end of January.

Broome is at its busiest in winter when you want to be there. All the cashed up grey nomads migrate there every year and have the CPs booked out every year. The Broome Shire also enforces no free camping. However, there are several farm stays and a CP not far out of Broome township (most you will need to drive to frolic in the ocean) and as well as being cheaper, the sites are bigger and cheaper.

Strongly you pay the $7 for a years sub to Wikicamps, if you don't already have it. This will show you all the free and low cost sies, plus the CPs with photos, cost and feed back of those who have stayed there.

There are few decent CPs in metro Perth - many have mostly permanents in them with few casual sites and charge a bomb (like most capital cities), but there are a few good ones on the outskirts of Perth, including one run by the Adventist Church (and no, you don't have to be of their faith) - this one is apparently a goodie, large sites and reasonably priced and not a long drive into Perth to sight see.

There are many good CPs in WA, a lot of which are independents, clean, tidy, relaxed, big sites and not expensive. Often they are run by the shire. But like the East Coast states, if you want to run alongside the sea, Dec/Jan is full of tourists and locals on holiday, CPs are often booked out, jammed up sites and expensive.

And remember to bring plenty of insect repellant. We have a fly and mozzie problem in WA and Ross River and Denge fever is slowly moving south from NT and there have been cases of these infections in Perth recently. And our mozzies are out day and night (just more at night).

Hope I haven't sounded too negative - you will love these parts of WA then, but do try finding CPs in the areas you want to stay now and book now