Viburnum - these prefer life on the moister side and are happy in shade. White or white flushed pink flowers brighten things up and often at an otherwise glum time of year. Sadly I'm giving up hope on one of my old favourites, Viburnum davidii, as I rarely see it without the nibbled edges thanks to vine weevil.
However, there is still hope and once again, this genus offers up multiple options for your needs:
Viburnum opulus grows to around a metre in height and spread and we recently used it for an informal hedge.
A client once commented that she loves Viburnums for the berries that the local peasant feeds on in the winter. I think she meant pheasant but this job really does yield no end of surprises.
Viburnum plicatum 'Mariesii' is a small shrub to approximately 1m in height and spread and has Hydrangea like flowers but these arrive in spring. Pretty to look at and I've yet to do anything to mine which has been happily going for 15+ years.
Cornus (or Dogwood) - Once again, this genus will surprise you with the myriad of forms they take. They don't like being moved or being too dry.
The most well known is Cornus sanguines 'Midwinter Fire' which is often planted next to the brilliant white stems of a Betula (Birch) tree so that, in the depths of darkest winter, the red stems really jump out. Cornus sanguinea is a good alternative to the 'norms' for a hedging choice although it will sucker so consider putting in a root barrier to save work in the long term.
For ground cover, try Cornus canadensis which is evergreen and will spread up to 1.5m once established (which can take a few years so underplant with as many as you can afford). According to The RHS, it originates from Alaska so no worries about our British winters. On the other end of the scale, Cornus kousa is a large shrub/medium tree or, if you've lots of space, go for Cornus controversa 'Variegata' (the Wedding Cake tree) which puts on a show like no other.
Perovskia - a little 'roundabout and car parks' these days but for good reason - THEY LOOK GREAT AND ARE LOW MAINTENANCE! Easy to grow from cuttings and will grow up quickly. Easily occupying 1.1m in height and spread; they have a wonderful way of taking over just as their friend, the Lavender, is going over.
Exochorda - another small shrub but this one prefers sun. Star shaped white flowers in spring.
Euonymus - there are evergreen and deciduous varieties available but the latter is our preferred form. You can see how, allowed to grow in the right space, it grows to a generous size and nothing is able grow underneath. Think how many perennials would be needed to fill the same space.
Pinus mugo 'Mops' - Definitely a plant which has gained popularity in light of the 'Box Blight' conundrum and really one we should have fallen for a long time ago. Can be allowed to grow haphazardly or clipped into neat mounds. Evergreen and drought tolerant once established.
Euphorbia - This plant is one we use time and again. First of all, there are just so many varieties of the plant for a variety of conditions! Need a big fat acid green presence?
Try Euphorbia characias subsp. wulfenii. Want spring interest in a shady spot? You need Euphorbia amygdaloides 'Purpurea'; Need an evergreen filler plant? Euphorbia amygdaloides var. robbiae is the one for you. Looking for early summer interest in a warmer colour? Euphorbia griffithii 'Dixter' it is!
Oh and the one thing they all have in common is a big fat tick in the architectural form box.
(A quick cover - they produce a skin irritating sap when cut so treat with caution (and gloves)).