A mission statement (statement of intent within an h&s policy) would be a 'to the point' description of what 'goals' an organisation wants to achieve as an whole. A policy will be more in depth and describe how you go about reaching these goals in detail. (i.e. who does what, how and when)

I disagree - a document that specifies who does what how and when is a procedure, not a policy.

A mission statement is what you want to happen - your goal. Normally fuzzy language with words like 'best' and 'market-leading'.

A policy is a succinct statement of what you intend to ensure will happen. Normally more specific language.

A procedure is the longer who does what, how and when document.

The term "policy" can mean different things to different people and it is best to be specific and refer to the 3 aspects:-.

Statement of Policy
The H & S Organisation Structure and roles/responsibilities
Detailed Procedures

If the mission statement says something like "we care about safety and will make sure we at least meet our legal requirements" then it acts as the 'statement of intent' that forms part of the H&S policy.

To my mind, if it acts as a statement of intent, it is a statement of intent. Although it could cause confusion if your policy is audited by anyone for any reason as they don't see something labelled as 'statement of intent' and they may wrongly criticise you for not having one.

Not forgetting the arrangements section of a H&S Policy.....