If any Ivy stems are mixed up in there, you will probably be pulling Ivy sprouts out for the next several years, so you will probably want to avoid perennials sensitive to root disturbance. Otherwise, I would brew a 48 hour batch of compost tea, about 2 gallons (8 l.) for every 9 sq. ft. (1 sq. m.) of ground up area, drench the area, and cover with more compost to 2 inches (5 cm) deep. Water once a week, if you don't get rain--and the ground isn't frozen--and by spring, the debris should be decayed enough to allow planting.

Thank you. Just the sort of advice I was after but what exactly do you mean by compost tea and how do you brew it for 48 hours??
Although it says I live in france on pm profile this is actually for my English garden in Dorset (mild and quite wet in the SW)

Simplest way to compost tea:

1 liter of good, black compost--home made is best, but commercial ones are good enough, as long as they are good and black.
1/20 liter of seaweed extract.
1/20 liter of fish emulsion.
1 20 liter bucket with a lid.

Put the compost in a fine mesh bag--an old nylon does well for that. Tie it with a string, and hang it the bucket. Fill the bucket mostly with water, add the seaweed and fish, and stir vigorously, Put the lid on the bucket, and let it steep for 48 hours, stirring 2-3 times a day.

24 hours brings up a good culture of soil bacteria, but 48 hours are needed to bring out the whole range of fungi, protozoans, humates, fulvates, and olmates needed to break down the wood chips underground.

For larger amounts, you can rent or buy special tanks with stirrers and aerators, but this method works well for the average home gardener.