Posted: 22/02/2015 at 10:21
What about a holly - they grow faster than people think but most varieties don't grow too huge. Lots of lovely ones here http://www.welsh-holly.co.uk/hollies.htm
The great thing about a holly is that once it's got to the size you want it doesn't mind being cut hard back into a formal shape if that will keep it to the required size, whereas many conifers don't like being cut hard back and you get left with brown instead of green foliage.
And of course, if you get a female variety you'll get berries for Christmas
(providing there's a male within half a mile or so , and there usually is)