Am I 'wasting' a south-facing border?

Astraeus

I have a 22ft length of a boundary, which faces due south, and as part of a garden overhaul I had in mind to plant it with few viburnum tinus shrubs to form a 16ft long hedge and an amelanchier x grandiflora. There is already an established magnolia in situ. My extant plan is to create a border 4ft wide up to our garden path, which I understand would leave no room in the border for anything other than the viburnum.

However, considering that this is the sunniest aspect of my garden, I wonder whether I am wasting the site to plant it up with a relatively shade-tolerant shrub such as the viburnum? Much of my thinking has been wildlife-centred but it occurs to me that it need not be one or the other in that I could possibly widen the border to 5.5ft so as to have the back of the border as the hedge and, in front of it, an annuals or herbaceous perennial border which is nectar-rich. Unfortunately the width of the garden will not permit me to go much wider than 5.5ft. Would this work? I don't want to have to prune the viburnum annually because it will stop it's profuse flowering, which was one of its attractions to me but it's ultimate spread can be up to 2m wide. Would that crowd out anything else in a 5.5ft border?

Still on the theme of the hedge, one possibility I had to give some variety and colour was to grow a group 3 Clematis through and on top of the viburnum so as to give me the early summer colour of the viburnum followed by the late summer colour of the Clematis and the berries on the viburnum. Is it realistic to expect a Clematis (possibly a viticella) to reach up through a viburnum?

On further consideration, perhaps this could be resolved by foregoing the viburnum and plumping for a more upright, less 'spready' shrub such as osmanthus X burkwoodii or berberis darwinii, both of which would offer the same early flowering and late summer berries plus a nesting site for birds.

Thanks for any tips, from a beginner gardener.

AnniD

To be honest, l think you could definitely do better than the viburnum in that situation.  My first thought would be the Osmanthus, but others may have better suggestions. 
 It would be nice to take advantage of the conditions that a South facing border provides , especially with regard to nectar rich perennials etc.
I'm afraid I can't really advise about the clematis, but there are very knowledgeable people on here who can 

JoeX

yes.

Fairygirl

Osmanthus and Viburnum are both better suited to shadier sites. O.burkwoodii doesn't have berries that birds are interested in either, as it produces very few. There are better shrubs if you want wildlife attracting ones. Berberis is ok, and Pyracantha would be better. 
If you're dead set on a hedge, better to pick one which will be happy being kept tight, like Beech or Hornbeam, and then you can have planting for wildlife in front - as @AnniD suggests. 
Better still - if you have a fence or some supports [or can put them in] just plant different clematis as the hedge.
Clematis will certainly climb through a viburnum no bother, but you'd struggle to keep the viburnum as a narrow hedge in the first place. 

Astraeus

Thanks @AnniD and @Fairygirl. Both responses are very gratefully received.

I am very interested in the suggestion of pyracantha as it is a personal favourite of mine but one which I had disregarded to some extent on the basis that it appears to have quite a spreading habit and thus afflicted by the same issue as with the viburnum. I do have a fence against which plants could be trained, hence my thinking being to maintain a low-ish shrub as a hedge with a Clematis above it, to extend the flowering season. I presume a pyracantha will be too dense for a Clematis to find its way through and above?

I am not dead set on a hedge but I am keen, in a neighbourhood which is otherwise given over to lawn, hardstanding or artificial turf, to give our regularvregular birds an opportunity to look to nest or seek refuge somewhere. Perhaps I ought to be looking at a pyracantha, if I can find one sufficiently upright and compact, with a Clematis atop. Or does pyracantha cope reasonably well with pruning, in that I could expect flowers or berries the year after it had been pruned to stay within a 1m spread?

Fairygirl

You can prune pyracantha no problem. Someone was asking about them only yesterday. You can simply remove any branches/stems which grow outwards. I do that with mine as they form part of the boundary 'hedge', which is rally just those and Buddleias. 
We were also discussing the fact that they can be cloud pruned etc. They're very accommodating plants. The more you hard prune them, the fewer flowers and berries, so it's one of those things you just have to bear in mind, but taking stray branches off is fine, and you'd always be leaving plenty for wildlife.
There are some columnar varieties too. I have a little red one in the front garden. You might need to look at online nurseries who will have a selection though. I think it might be called 'Red Column' - strangely enough 
Clematis are actually 'designed' to grow through shrubs etc, but it's just that we tend to grow them on fences, walls and trellis etc, so that we get to see them 
All you'd have to do is make sure you plant them far enough away, so that there isn't too much competition for moisture, but that will also depend on what your local  climate is like.