I had cauliflowers and winter swedes to follow my onions and my potato bed was followed by a second wave of dwarf beans and quick maturing peas. I wont have any spare ground until later.
How about sowing a green manure crop while you still have the warmth and rain, then mulch the green manure with the manure to kill it off and let the worms do the digging over winter and turn the bed over in spring next year - if it needs it; probably won't.