I would double dig and wait for the frosts to break it up having added lots of compost and some manure then leave till the spring. If you want to plant at once add compost and Blood fish and bone.

I would add some general purpose compost and then blood fish and bone to each hole I dig for each plant.

I'd dig it over with a garden fork to break it up, removing any celandine, clover and dandelion roots as you go, and then incorporate well composted manure or soil conditioning compost from the garden centre, or lots of good garden compost. Let it rest 8/10 days or so to settle, and then plant if you want, first broadcasting something like Growmore or Vitax Q4, or putting blood, fish and bone in the bottom of each planting hole.