From an old issue of Garden Gate:
"Designing a Victorian-style carpet bed isn't too difficult. Simply draw out a pattern on paper and plan for maximum color contrast.

In general, simple designs best. Once you've decided on a pattern, the next step is to recreate it on the ground. Victorians sometimes used templates. You could make your own by cutting out shapes of cardboard. You'll probably also need to use a tape measure and a garden hose. Once a bed's prepared, lay out the lines with the hose or the template and then use flour or spray paint to outline the pattern in the bed. Mark the entire bed first so you can stand back, visualize and make adjustments before you plant."

And not to be overlooked...the position of the bed should be so that the viewer can look at it and actually read the business name... on a mound or bank.

Since you're in the UK, you have a better idea of avalable annual plant material. Blue and yellow - pansies might be a good choice and lots of them planted close together for maximum impact. Blue pansies as a background with the company name tricked out in yellow.

Key phrase "carpet bedding".