Well I'll tell you what I did and it really solves all the problems - I hired a gardener. He's worth his weight in gold. Really, his rates are very reasonable. He comes in every other Thursday to keep things in check. Whether I'm home or not, he comes. He cleans up the clippings as well.

It sounds like the deer aren't spending as much time in there as they used to. It may be caused by a pack of feral dogs, or possibly by the surrounding land becoming more populated. If they can't be lured back with a salt lick or occasional piles of alfalfa pellets, you may have to let someone's goats run in there for part of the year. It may also be possible to arrange with neighbors for a safe and quiet corridor to a larger tract of woodland. Local wildlife managers will probably have better ideas than mine, though.

Maybe get the local wildlife trust in and look at the various habitats and how it could be better managed for wildlife which might mean tweaking here and there and cutting back the dominant plants.

As its too dark, ask a tree surgeon to assess it and remove some of the trees. Use the felled trees to build habitat piles for the wildlife. Asking your local wildlife group is a good idea as they may be able to offer solutions and perhaps some volunteers will help.

Strim down the nettles and remove some of the brambles. They are both essential wildlife plants however. Is sticky willow the same as sticky buds/Annie/Willie cleavers/goose-grass? If it is the time to tackle it is early in the season before it flowers and sets seed.

Perhaps get initial help in clearing what needs doing so that you are able to keep on top of it in the future.
Has fencing been put in elsewhere that is keeping the deer away.

All the wildlife including deer are still in the wood - that’s not the problem. The problem is it’s nice and habitable for the wildlife but not for us!! I think I’ll just have to clear the undergrowth a bit to make it more accessible for us and maybe remove a few of the conifers which are all completely bald at the bottom anyway with the only growth reaching to the sky and blocking the light.

Chances are, thinning out the canopy is only going to make the undergrowth thicker. In fact, I was wondering about the overall health of the trees, and if the canopy is thinning out already, due to introduced pests and diseases.