Kentmere was and continues to be a manufacturer of sensitized paper in the UK. They used to market their products through Luminos in the US.
Luminos has decided to abandon silver-based photography in pursuit of digital alternatives. When that happened, Kentmere opted to market their products under their own name. In addition, they are now private-labeling for Freestyle (and perhaps others).
AFAIK, the current Kentmere line includes everything formerly offered by Luminos, as well as products that Luminos did not carry - with two very notable exceptions. Kentmere's business is based on coating papers with photosensitive emulsions - they do not manufacture the base paper stock, but rather source that from other suppliers. Two of their former products have been discontinued because the manufacturer of the base stock chose to discontinue that product. The latest issue of Black & White (UK) that I was thumbing through a couple of hours ago at Borders mentioned that Kentmere is continuing to look for an alternative supplier for that base paper.