Here’s a list of some leading national suppliers of kitchen unit door knobs in the United Kingdom:

```markdown

Leading National Suppliers of Kitchen Unit Door Knobs in the UK

1. Hafele UK

   • Specializes in furniture fittings and architectural hardware.

2. Samuel Heath

   • Known for premium quality door hardware and fittings, including kitchen knobs.

3. Brassware Outlet

   • Offers a wide range of brass kitchen knobs and fittings.

4. Graham & Brown

   • Provides decorative hardware solutions, including kitchen unit knobs.

5. Toolstation

   • A supplier of various building and DIY products, including kitchen fittings.

6. B&Q

   • A popular home improvement and garden center with a variety of kitchen hardware.

7. Homebase

   • Offers a variety of home improvement products, including a range of door knobs.

8. Dunelm

   • Known for home furnishings, they provide various styles of kitchen knobs.

9. Wren Kitchens

   • A major supplier of kitchen units which also provides matching fittings.

10. IKEA UK

    • Offers a wide selection of kitchen hardware, including door knobs.

```

These companies are recognized players in the market and provide a variety of styles and options for kitchen unit door knobs in the UK.