Trees, Shrubs & Weedkiller

I've planted non-hybrid cotoneaster & honeysuckle for autumn berries and a silver birch so looking forward to them growing-up and providing food for my winged visitors. Am wondering what shrub to plant next? I think viburnum will be too big...maybe holly? Unfortunately I've used Roundup on ground elder and sycamore which have been taking over but once got rid may try the home-made weedkiller. Any advice welcome :-)