I suspect it would very much suit governments to force children into school earlier. They seem to have an agenda to create a compliant, dumbed-down population of worker-consumers ruled by institutions.
I’m not sure that complaining about individual nurseries is the way to make change happen. Such complaints will only have two outcomes. Local authorities' first step is to 'coach' the nursery’s management: essentially, they show them how to stay within the rules whilst still charging parents the same amount by other means, or shift the burden to non-funded children (anybody fancy double fees for the under-3's, for example?) It could ultimately in nurseries being refused funding, in which case parents lose out and/or that particular nursery loses business and eventually closes.
None of this puts any pressure on central government to fix a system that was clearly already eve, but before he political parties turned the 2015 general election into a bidding war for fools who were prepared to sell their vote in exchange for an empty promise of under-funded 'free' childcare.
The government has already got its quid pro quo for this ridiculous policy, and is very happy for childcare providers to take the unpleasant consequences whilst spinning how "successful" it has been.
IMHO the only way providers could put pressure on government would be if they all organised a mass boycott of the scheme. But that’s not likely to happen. Providersreally don’t want to hurt families, not even in the short term; also, some nurseries would lose too much business if they boycotted the scheme whilst other local nurseries participated.