Hostas are best planted in spring in my experience which gives you time to find a supplier who will deliver by post or a nursery you can visit to selcet plants yourself. Check out the RHS plant finder facility on their website.
For stones and pebbles, best to go to a builders' merchants where prices will be better than in a garden centre. If you buy enough, they'll deliver.
This may be a long shot but does anyone know what the plant that covers the ground in the photo below is called?
celandine? invasive weed but there are some forms that aren't so bad and are a bit more decorative.
If the little yellow flower in the top left of the pic is attached to it, it's Lesser Celandine (quite invasive)
I'll have a look at Celandine family and see what varietyies are not invasive. Seems like a nice plant and reminds me of my tropical aquarium in which I had a plant called Riccia which formed a lovely lush carpet.
Some pictures of the garden.
Before it was covered in grass which was horrible looking and stumps
And after much work of sifting all the roots from the soil with a shovel and by hand and planting some of the plants that will go in it the garden looks like this: