How about an Astilbe,A.man..they prefer a shady spot and spread well,with good height..although you would need to dig in plenty of humus rich soil..and keep it well watered..One of mine is called Astilbe chinensis var.pumila..it says it is a dwarf ..10x12" height and spread,but it most definitely isn't,as it gets quite big..

There's a green and gold euonymus that will grow tall and slender albeit rather slowly - somebody might recognise the one I mean. I have an almost identical plot by my shed and I have a mahonia Charity at the back (which you wouldn't have room for though) and the euonymus in front of it, with geraniums and epimediums in front of them.(The biggest epimedium is in just the same position as yours - snap!) If you try an astilbe in a dry corner put some water retaining gel crystals in and around the planting hole as they get very miserable if they are too dry.
Could you perhaps train that hydrangea to grow a bit lower - that might be enough for what you're after.

Or if you are looking for something to replace the plants you "just put in", there are several nice variegated eunymus fortunii shrubs which are attractive and bright all year and they will even climb up the wall if you plant them at the base of it

I have white aconitum in shade under a beech tree. it does ok. at this time I also have pale tall aquilegia and they do well.

How about Daylilies (Hemerocallis). They tolerate shade and come in every colour except blue. They flower from simmer onwards to early autumn.

Two suggestions - Dresden Doll, flowers are apricot pink. Devon Cream, flowers are lemon yellow.

Bloomer - I love astilbes and will probably plant one in there taking on steragram's advice about the water retaining gel crystals.

Steragram-have got euonymus plenty in my garden but mahonia looks promising. Will have a look at that hydranea and see if I could get it to grow into the "gap".

Seaburngirl-not familiar with aconitums at all. Are they easy to grow? Acquilegia's spread like wild fire in my garden so trying to control where they grow as only seem to have dark purple ones and would like to have more of a variety.

Bendipa- never thought about daylilies. Are they prone to visits from the dreaded lilly beetle? If so I have quite a few

Many thanks for all your suggestions.
of them in my garden so that would be a no no!

I wouldn't grow hemerocallis in full shade they do ok in part shade but they do perform best in full sun, they aren't bothered by lily beetle but the early varieties can be attacked by gall midge, their only real pest, later varieties aren't affected.
That Hydrangea Petiolaris is stunning!!! its taken mine years to get to a decent size

Simbad- when we bought our current house I fel totally in love with the garden, the house didn't really come onto it!! The garden has afabulous feel to it, mature and private. It has several mature climbers around the garden. Lost a couple of ivy a few winters ago but have replanted and its coming along now. For more pictures go my latest blog to get an idea of my garden.

According to that photo it looks like you have some light coming in (about 1pm). As long as the area is not continual dense shade, then Day Lilies will do fine, although they flower best with some sunlight. Even then they are grown as much for their sword-like foliage as for their flowers so if grown purely as a foliage plant then deeper shade won't matter.

Two shrubs that do well in medium shade as well as brighter areas are Viburnum Tinus and Berberis Darwinii, and both will take up a fair bit of space when mature up to 2m tall and flower well in spring. Both have dark green, glossy leaves and are evergreen. If you want a purple leaf Berberis there is B. Thunbergii Atropurpura and that does well in shade and grows up to 1 m high, but it's deciduous.

Last but not least there's the Cornus Dogwoods with their showy maroon, yellow or orange stems in winter.

PS. Be careful about considering Aconitums as the plants are deadly poisonous.

Aconitums like many plants are poisonous but I don't suppose Amsterdam is planning to eat them! Daffodil bulbs are poisonous but unless you mistake them for onions.....

I grow many daylilies and find they perform best in full sun (see my garden pictures),why grow a plant that has such beautiful flowers just for the foliage when so many plants thrive in shady conditions?

Quite a few roses grow in shady conditions as long as as you get some sun there. I grew Mme Isaac pereira and Souvenir de Dr Jamain, with less then 2 hours sun a day they were climbers though but fantastic flowers all summer and that fragrance...