My back garden has a small, paved area with high walls all around it. How can I make it a more inviting, green space?

Any plants will make the garden more welcoming. You could also paint the walls a pale colour to reflect light and highlight the plants you grow. Concentrate on growing climbers and wall shrubs, such as flowering Ornamental Quince, Euonymus Fortunei and Dwarf Clematis, mixed in with other climbing plants. In front of these, have smaller shrubs and perennials, such as Sedum Dianthus and Catmint. Add colour with hanging baskets and pots filled with perennial shrubs.