What To Plant Under Holly Bush On Small Slope?

evismail

We have cut back this holly tree/hege which began to overtake the lawn at the rear of the garden. This, together with the ivy on the far right. There's not much more we can do with these two hedges seeing as they're on our neighbours plot (we'd love to eradicate the ivy!). If you have any further advice on our pruning, we are all ears .

This bank is West facing and gets the sun from around 2pm until sun set. We don't want the holly to overtake the bank again as it makes mowing the lawn a pain. However, we also need to do something with the soil bank. Not sure whether there's a need for a retaining wall, or just some ground covering plants? But what would grow well under this established holly?

All ears and all suggestions are very much welcome!

Fairygirl

Unless you live in an area of high rainfall, you might struggle to get anything established there.
My suggestion would be to put a simple retaining 'wall' of timber/block/sleepers [whatever's easiest for you ] and then backfill with decent soil and plenty of well rotted manure. That will give you a decent medium to plant into. The ground will be very depleted of nutrients, so make sure to enrich the soil/planting hole each time you plant something too.
When you plant, water really thoroughly, and then mulch with bark or similar to help retain moisture. Keep everything really well watered until established. A bit tricky this year unfortunately! You'll probably still need to pick plants suitable for dry-ish ground, but there are plenty.
You'll be able to grow a lot more if you can improve the area, otherwise you'll have to stick with things which like poor soil and very dry conditions. 
I also should have said - keep a space between your plants and the holly, perhaps with a few slabs or simialr,  as you'll need to get in there now and again to keep it pruned back.