UKH

Any hints , tips and recommendations when looking for somewhere to stay and who to go through. Requirements 

Catered chalet

12-18 people

Pretty big ski area

Outside of school hols

Not too posh i.e not too pricey

Sooooooo many choices, any particular country and approx budget ? That might be a starting point. 

As no one else has chipped in.

Iglusk.com is quite a good aggregator of option. I would fix a budget and try and fit to that otherwise your question is a bit of a needle in a haystack.

As for the rest, you could narrow it by 'big ski area' to one of the 'big ski areas' - Trois Vallees, Val D'isere/Tignes, Sella Ronda (depending on time of year, less snow sure). 

Then look at cheaper options within those areas - these will often come with a 'character/atmosphere' trade off relative to the more expensive, and sometimes have poorer access to the skiing (some of the lower Trois Vallees resorts).

Anyway, hope that's a bit of a help.

Recently the group has done switzerland and austria in hotels with about £750 to 1k half board all in but aware we may have to be at the top end or even above that.  But any decent european resort woud be ok.