You're almost right, but not quite there!
Legally there is no requirement for consent to publish in this country, with a few minor exceptions such as Sect 85 of the CDPA1988 and in a very, very few cases Art 8 of the HRA 1998.
Likewise in this country, there's no legal difference between a photo published for editorial use or one used in a commercial.
The huge difference is what the photo implies.
In the UK, specifically in England and Wales, we have one of the loosest set of defamation laws in the world ( although that's in the process of being changed) and this is the principle threat to commercial use.
If a photograph implies that a person endorses a product which they may not, then there is a possibility that they can bring a defamation case.
That's what consent forms ( model release is really poor wording derived from the USA) protect against.
It doesn't even have to be a seperate document, as consent would normally be written into a contract.
That applies to adults as well as children.
There are a few, rare, circumstances that may affect a publication, such as a court injunction and/or a child protection order, but most people won't get anywhere close to being affected by these.