Posted: 24/10/2015 at 08:21
As pansyface says, anything growing quickly isn't going to miraculously stop at a couple of metres, so it's best to decide whether you want something attractive which will take time, or just something fast growing which you'd need to prune and trim regularly. If it's the latter, you may want something you can turn into a topiary specimen, such as yew or box. If it's the former, something which will provide flowers in spring or summer but also some autumn colour to extend the interest.
Buttercupdays has given you some good choices already, and I'd also add Amelanchier lamarckii for flowers in spring with berries and good autumn colour later. The spindle tree Euonymous alatus is renowned for autumn colour too. Sorbus ( Mountain ash not Whitebeam) have spring flowers with berries to follow and good autumn colour. They all get bigger than 2metres but they have light canopies. There are also shrubs like Hydrangea which would be happy there. For a specimen, I'd go for something with a good strong shape as a main priority.