It depends how high you want them to grow and how much effort you want in future years to keep them under control. Whatever you do, don't plant Leylandii!! How about a mixture of species with different leaf colour/evergreens etc. Also, how thick does the screening need to be ( hiding a building/for privacy?) Some of the best subjects may take longer to fill the space but will be more satisfying for longer.
Also, do you want it to be a crisply cut hedge or a looser, more informal affair? So many questions, I kinow, but otherwise we don't know what to uggest for the best. Add your reply to the bottom of this question page and we can continue.....

Wish to fill a 15m space with bushes or trees to screen houses. Any suggestions?

Eucalyptus grows fast and is evergreen (or blue), One or two conifers in the row would be nice (Cupressus macrophylla Gold Crest maybe), silver birch is fast too.

Hi, Thanks for your reply, we wanted to plant something minimum 5ft to give privacy from neighbour's house. Would like evergreen, either trees or bushes. Not too crisp but perhaps with a bit of colour. Was thinking about Viburnum Tinus but cannot get the plants higher than 3ft. Would like the screening to be fairly thick, possible growth to a maximum of 8m. We have a very large Christmas Tree at the end of the gap. Did think about skyrocket conifers but thought it would not look right with the Christmas Tree. Hope this helps and look forward to hearing again. Many thanks.

I rather like Physocarpus 'Diablo' for a bit of colour and easy to manage or Osmanthus burkwoodii.

Elders grow quickly and can make a lovely screen e.g. Sambucus nigra 'Black Lace or Black Beauty. However all the above are deciduous but they thicken up nicely and make good homes for wildlife.

Or how about an Escallonia, they flower nicely if not trimmed too regularly and are evergreen. They grow to about 2 or 3 meres so not too tall. Try to avoid anything that gets much taller than you really need as you will spend ages trimming it back every year. Skyrocket conifers are quite narrow and don't grow very fast so would look small for ages. Viburnum tinus is a bit boring....dare I say it!! Although good if in a shaded area. For fantastic autumn scent (also evergreen and fairly quick to grow) how about Eleagnus x ebbingei. There are variegated ones too.