Is it possible for me to manufacture and sell items which have US Patents but no EU Patents? I realize I cannot trade to the USA and only intend to sell within the UK. My main question relates to the fact that the US Company now has a base in the UK and is trading from it, however their patents are only US.
Your products may not enter the soil of any country with patent protection for the product without a license. Please make sure there no other patents in the same patent family or similar patents. An invention normally has more than one patent protecting aspects of it.
Other than that, you might have to make sure that your customers don't import the product into the US. With consumers this might be impossible but rather negligible, but if you sell B2B this can become an important point. (I'm not sure about the exact laws there, but just selling in the UK and not caring about this is - afaik - not enough).