I'd like a clearer idea of what you mean by 'very large' pots - also whether you're standing these pots in full sun, half sun half shade or in full shade before plunging ahead with a list.

Some tried and tested plants fo you to muse over here,

Aucuba, Viburnham Tinus, Phormium [large pot rqd],Ilex, Skimmia japonica rubella, bamboo, elaeagnus, ceanothus, hebe, Acers[ leaf change], fatsia, camellia etc, but remember the situation is vital to some of the plants, however i have created a similar effect in part of our garden, but have incorporated some deciduous flowering shrubs, so i get interest through the seasons, the situ of these plants are in semi sun, i root prune most every couple of years, just a point, they will need feeding and watering, when you are away will you be able to keep them watered. julien

Hi Bamboo
Pots in question are approx 4ft tall and 2ft dia a couple slightly larger. Some are in full sun and some in dappled shade. We are in our early 60's ,have moved around a lot and have never had the opportunity until now to create a garden of any sort. The area where the pots are has conifers on two sides, a large stone circle in the centre with a 5ft Italian style water feature and flagged areas with green slate chippings inbetween. We are looking for plants with impact and which give colour all year. Currently have small pots dotted about which look completely 'lost'. Two of the pots stand either side of the entrance to a flagged bbq area.

I know it's not a shrub, but I have a Euphorbia characias wulfenii in a pot and it looks good at all times of year, including throughout winter.

Hmm, nice, very large pots indeed, Bez. For the ones at the entrance to the bbq area, how about lollipop bay trees? Or maybe toparied Box or something.
I'm sure some of the following have been mentioned already, but here goes anyway:

For shadier spots, and acid compost, Pieris Forest Flame, Skimmias (you'll need a male and female, so two at least, say Kew Green and Kew White (white berries) or Nymans for red berries, or get S. reevesiana, which is self fertile), Camellia (recommend red flowered, the paler flowered ones show the brown spotting as they age much more readily), Rhododendron, Fatsia japonica (this one doesn't need acid compost).
For sunnier areas, Phormiums, Trachycarpus fortunei, Phyllostachys nigra or aurea (bamboo), Euonymus aureopictus, Viburnum davidii, Prunus cistena (will need regular pruning). All mentioned so far are evergreen bar the Prunus. Then there's the smaller things like Lavender, Deutzia, Spiraea japonica 'Goldflame', plus possibly flowering perennials and bulbs - most of this list isn't there for their flowers!

Thankyou all so much for your valuable advice. It has certainly narrowed down the choices which is a bonus as I don't have a great deal of time. I shall however take the time to go on the internet and browse all suggestions. Thanks again