A model release can limit the possible usage of the picture. For instance the model can state, in the release, that the image cannot be used to promote the tobacco trade, the fur trade, the weapon trade etc.
The model can also state that the picture cannot be used in a defamatory way, but this is often considered implicit, a "defamatory" use would require a specific release.
I don't know if the person meant that. That is something that as far as I know is true in most countries, I don't know what the specific laws in the UK would be, I'm actually quite interested in knowing better the specificities of the UK in this regard.