I'm not sure how we compare on mental health, but I am in France and we generally get 8 weeks; beginning of July to beginning of September (also 2 weeks in Oct / Feb/ Easter)
I also can't speak for the whole country but locally to me, childcare during the holidays is high quality and reasonably priced (on a sliding scale for income).
All childcare in my village (we are outside a city / not rural but the old village boundaries/ local mairie still exist) is run by a community association, non profit. The association employs staff who are qualified and it's their full time job and it's the same people who provide the wrap around (before / lunch / afterschool provision).
It's full time for primary and there is an afternoon club for teens.
for the primary age, there is always a mix of activities, free play and days out (no extra cost). Sometimes a parent or 2 will help so they can do bike ride / picnic day or trip to the local swimming pool.
For the teens it's a bit more just a safe place to hang out / there is a teens chill out area, games, music. When my daughter was there, they did a bike ride/ wild camping night (again no extra cost).
Ultimately, I think it's a cultural thing. A lot of provision (sports, theatre, music etc) here is fully volunteer organised which means that cost is low but equally almost everyone I know volunteers in some way.
Our childcare provision, which employs staff, is managed and run by dedicated volunteers.The volunteers change as children get older, new parents join and older volunteers move on
It's a big commitment but everyone just does it, its the french way, everyone contributes (the fraternity part of the devise). I feel very fortunate to have benefited when mine were small but I don't know how you could make something like this viable without the non profit / volunteer model and the culture isn't the same in the UK.