Question regarding home contents insurance

[StackerNoob]

Hi folks, 

I'm looking into a new home contents insurance policy for moving house. I haven't delved into too much detail as yet, but I wondered what everyone's take is on PMs. 

Some policies state that any items below a certain value (say £10k for example) do not need to be specifically declared in order to be insured. Some make specific mention of PMs in all cases, but its not a universal thing.

I don't ever have all my metals with me in my home anyway, but every now and again I may have a significant proportion on me. 

Does anyone know if a collection of anything, including PMs, is considered a single item, or if the individual pieces are the individual items from the policy point of view. I imagine people up and down the country have collections of things that, individually, hold no real value, but collectively are very valuable (like trading cards, antique sets etc). How does that work?

Any insight here would be useful. And any recommendations for insurers also useful!