advice for newbie

Hi all- I'm new to the forum, joined a few weeks ago and have just read posts. My profile will tell you that I'm a new gardener living in Kent. I'm posting here because although I haven't got an allotment, in June I inherited a roughly square 70ft x 70ft garden. It had not been cultivated for about seven years. It is more or less South facing on a slight slope. Most of it was grass with some nettles but not a lot of other weeds except one side has bindweed. There was a section with a lot of raspberries which had a lot of fruit but neighbours said they were ten years old so I have cut them down and discovered brambles every where. I cut the grass as low as possible and covered most with black plastic. I had three 6ft x 2.5ft bookshelves I didn't need so I took the shelves out covered the back with membrane filled with compost(bought) and used them as raised beds. Carrots, turnips, lettuce, spring onions and beetroot grew well. I've now got onions and garlic in them. I also uncovered a bit of the grass and have broad beans growing well. Now for the questions.
There is a 5ft high wooden fence at the bottom of the garden which is a bit bare apart from nettles and a plum tree which had no fruit, partially shaded and a little damp. What would I grow there?
I have just received my seed potatoes. 10 earlies, 10 second earlies, 10 main crop. How should I store these and when should I put them out for chitting. I do not have a greenhouse but there is a shed with a window. Sorry for the long post but I thought the info would be useful.