The United Kingdom can always use more revenue by selling public forests and national parks. Some can even be used for logging rights or mining rights as the gift that keeps on giving. If Great Britain needs austerity measures, selling off some of its non-essential assets can be a way to shed liability and earn more revenue.
Too much land is already privately owned. When I was a kid I was allowed to pretty much go anywhere I wanted to with no worries about being on someone else's property. Now it's hard to let kids walk through the woods without worrying if they are on private land. Parks and forests should be kept national, not private so that people still have areas they can freely roam and enjoy without fear of trespassing.
If the United Kingdom begins to sell forests and national parks to private concerns, then they are going to be developed and probably not in a way that enhances our environment. We need open space as a culture and the country needs to do what it can to preserve this resource.
Wildlife needs to be protected and maintained. Humans are populating this world like crazy and we are running out of natural forests and places to visit. It is important to hold onto the land we have and keep national parks. They give money to the government while also giving people a place to visit.
I do not believe the UK should sell or privatize its forests and national parks. These areas are designated so that they can be protected by the government entity. If they are sold or privatized it will open them up to degradation and uses they were not meant for. It is best to keep them protected.