I guess that evergreen is therefore important as there are many more far more attractive deciduous shrubs and trees you could use with better foliage and flowers.
Of ever green, laurel would be more attractive than leylandii and better suited to pot culture, or you could even consider bay trees. Rosemary will grow to 4ft if pruned correctly and well fed and will give you wonderful flowers and scent in the spring and late summer. Personally I like Jersulam Sage which will certainly grow to 4ft.
An alternative would be to erect a simple trellis on which you could grow attractive climbers from various clematis to Russian vine if you want something very vigorous.

Anything but Leylandii! This is both ugly and high maintenance. Yes, it is quick growing - but then it keeps on growing untill it reaches the sky, or so it seems, unless regularly kept trimmed.

And once bits of it go brown as they do it will not regenerate,,

For that many pots permanently you may want to consider an automatic watering system

Juniper is one to consider. They do not mind being in pots and you can get various varieties of them in different colours and shapes.

Thanks to you all who replied to my question they have been most helpful and work can start tomorrow , weather permitting of course

Use a John Innes based compost for permanently growing shrubs in pots. Its got a better structure as it is soil based. It is also heavier so the pots won't be so inclined to blow over. However, bear this in mind and fill the pots in situ!