Sedum specatbile, would look nice and as the summer progresses you will have some lovely salmon pink large flowers late summer into autumn, lisimackia clethroides, phlox, aster, japanese anemonies, or why not choose a cornus midwinter fire keep it small so you have lots of firey stems at the base of the stems through winter so many options you could choose from.

Thanks for the quick response Julien. Just checked lisimackia( never heard of it) and it mentions that it could be invasive . Have you found this so?
Would you plant the same breed all round the standards and if so how many plants.
My border is about 80 ft long and in its 5th year but still have too many gaps of soil. I do grow loads of annuals and they do eventually fill up .

What about smaller shrubs around, or must it be herbaceous perennial? Is the area where the Skimmias are planted shady? And yes, Lysimachia is invasive.

No Bamboo it doesn't really have to be perennial. The border is west facing. Have you got any shrubs in mind.

Spiraea 'Goldmound', Sarcococca hookeriana, Weigela nana variegata, Senecio 'sunshine', Euonymus fortunei 'Emerald'n'Gold', Fuchsia Margaret Hunt or Mrs. Popple are a few possibilities. Google 'em, see if you like any of them.

Thanks Bamboo. I have got some of those you mentioned in other areas of the garden and never thought about them for this problem. I do like the Weigela .

Yes the lismackias can be invasive but not over night after a couple of years just reduce the clump sizes, the ones i use are Lismackia, punctata, clethroides, white flowers curl at the ends a real show stopper along with lismackia ciliata, beautifull burgundy foliage with yellow flowers, mix with a few other shrubs, what does go well next to skimmias is osmantus looks a little like varigated holly but quicker in growth.