UKC

If one wanted to go somewhere 'in-season' to climb some moderate routes on big mountains in December-January, where would you suggest they go? My research so far has suggested either Anconcagua and surrounding area, or the Ecuador volcanoes.

I like the sound of Anconcagua by the Polish Glacier Direct - it seems like the right size of adventure and difficulty - but alternative suggestions would be very welcome. Ecuador is less appealing only because of the requirement to have a guide. I'm only interested in self-sufficient and unguided ascents.

Is there anywhere else that I should look at?

I'd personally be off to Mount Kenya like a shot; it's been on my list for decades. Jan/Feb is ideal weatherwise, and the Kenyan highlands are beautiful. The ice routes have apparently become dangerous, but there are loads of good rock routes. Check it out:

https://www.summitpost.org/mount-kenya/150259

High Altlas

If interested in more alpine-style ascents I would go to New Zealand. Jan/Feb is prime time for the big peaks (Cook, Tasman, Aspiring etc)