Posted: 06/03/2013 at 23:00
You're not too late! First things to get in I think would be broad beans, onion sets, early peas, strawberry plants. Too soon for lots of things like runner beans, French beans, sweet corn, courgettes, nearly time for potatoes - 2 or 3 weeks, but you want the frosts over when the green leaves appear.
Fresh manure is not a good idea. Leave it in a pile for autumn. Get some compost if possible and organic fertiliser.
Not sure about shallow soil if it's on tarmac. What's the drainage like?