Ideas for below lollipop privet

Hi All, I recently planted a lollipop topiary privet next to our front door, in a raised bed which is approx 75cmx75cm. Privet looks good and is growing like the clappers, but my mind now turns to - what to do underneath! Especially as the local cats are very pleased with their new toilet! Soil is clay to heavy clay but I have improved as much as I can (25+kg of well rotted manure etc) and the raised bed improved the drainage, as does being on a slope. The site is North East facing, and does suffer from heavy winds and is relatively exposed in winter. I'm in Sussex so it doesn't get too cold but does get a bit battered around. I could just put slate chopping a around and be done with it, but I was thinking I could: - plant a lavender hedge around the bottom edges - plant some campanula as ground cover Anyone else got any good ideas for what would look good under here? General theme is blues, purples and an accent with white.