Ok,one of the main things you will need to do is replenish the soil.If slabs have been down for a while,it is likely to be in pretty poor condition.If you have a farm or stables nearby,well rotted manure would be the best & cheapest option.Otherwise any sort of organic matter dug in will improve it.
I would imagine both wall & fence would be ok for climbers,as long as they are planted at least a foot from the base of the fence/wall.Any closer & they will suffer from being in the shadow of the wall & won't benefit from rain ect.On my north east fence I have successfully grown clematis,rose 'golden showers'Ivy,Jasmine & honeysuckle (oh & raspberries & rhubarb).On the Northwest wall, try Solanum (potato vine)climbing roses & clematis again.Also any type of Ivy will be fine,but varigated types don't do so well in shade & loose their colour.Clematis like to have cool roots,so putting a slate or mulch over the planting hole will improve youir chances of success with them.
Ground cover & plants for borders could be;
Buxus sempervirens-Box
Daphne laureola
Eleagnusx ebbingei
Gaultheria shallon-
Hypericum x indorum
Lonicera pileata
Mahonia aquifolium
Osmanthuis decorus
Ruscus auculeatus
Viburnum rhytidophyllum
Vinca major -blue periwinkle
Vinca minor -blue periwinkle
Alchemilla mollis-ladies mantle
Epimedium pinnatum colchicum
Iris foetidissima
Tradescantia zebrina
For summer bedding or to brighten up dull spots,Busy Lizzies will flower in shade & are tough little things.
As for the veg patch,the best place is likely to be in the centre of the garden,to maximise the light & sun.I don't know how you feel about a 'potager' type patch,but it could look very pretty,with all the veg set out ornamentally.If you like the sound of this I can do you a list of veg that looks good as well as tastes good ie purple carrots,red & white beans ect,purple kale ect.
Let me know if I can help anymore