I would say that if the product originated in the UK and is still made in the UK, then it is not a foreign product. If the product originated abroad, but is made in the UK, then it is a foreign product. For example, Cadbury is no longer a UK product, although the company originated here, although, say, Montezuma's, which is UK owned and sold, is a UK brand.
I thought most stuff was made abroad anyway these days? The UK used to be one of the shining lights of the chocolate industry, but not now.
Hope that helps...