Here's a list of businesses (and their ratings) in the Manufacturers/packers category.
In England, Wales and Northern Ireland food hygiene ratings are provided by the The Food Hygiene Rating Scheme (FHRS). Ratings in Scotland are provided by a similar scheme called the Food Hygiene Information Scheme (FHIS).
You can read more about FHRS and FHIS food ratings here.
Click on a establishment below for more information:

Total Score: 15 (lower is better)
Wow Workspaces 10, Unit 4 Mowat Industrial Estate, Watford, WD24 7UY

Total Score: 0 (lower is better)
PERFECT HYGIENE RATING SCORE
Intu Watford, 135 The Harlequin, Watford, WD17 2TJ

Total Score: 5 (lower is better)
Unit 9-10, Trade City Watford, Thomas Sawyer Way, Watford, WD18 0GS

Total Score: 15 (lower is better)
Langley Bites, Gade House, 38 - 42 The Parade High Street, Watford, WD17 1AZ

Total Score: 20 (lower is better)