I'd suggest Sambucus 'Black Lace', which is extremely easy but wonderfully attractive with pink/white flowers in spring, purplish foliage, and wonderful dark berries in autumn (which you can eat in pies or as part of a 'summer pudding'). Easy to propagate, and kept in check with strict pruning will remain as small as you want it.

Evergreens: Mahonia aquifolium, Mahonia 'Charity', Berberis darwinii, Brachyglottis (used to be Senecio 'Sunshine') Skimmia, Pieris forestii, Photinia fraserii 'Red Robin', Choisya ternata 'Sundance', Sarcoccoca varieties, Euonymus fortunei varieties, Phormium , Hebe'Youngii' (all these look good year round)
Deciduous: Cornus alba 'Sibirica variegata' Berberis thunbergii atropurpureum, Berberis ottawensis, Cotinus coggrygia Royal Purple, Spiraea 'Goldflame', Deutzia, Forsythia, Ribes sanguinum
Maybe that's enough for now - you need to check out what they look like and sizes to decide

It's been pointed out to me that I neglected to say that, if your soil is chalky or alkaline, Pieris and Skimmia won't like it - they prefer neutral to acid, so if your neighbours grow rhododendrons, camellias, blue hydrangeas, both pieris and skimmia will be fine in your soil. I didn't say it cos I thought I'd said enough, otherwise it'd be a dissertation, lol;-)

dont forget escalonia too. good list there bamboo :o)

As it's north facing, I would include a sarcococca - these are evergreen and flower in February with VERY scented flowers

Wow! thanks, off to garden centre now, am guessing will need my credit card!!

No, hold on - you need to check them out first before buying - check heights, widths, leaf colours, flowers etc, lol!