UK Gov has a good few schemes to help out people who want to plant woodlands, you can get grants for developing a woodland management plan, along with help from the Forestry Commission in setting up a plan that makes sense for your land. link
They also provide grants for woodland creation, with funding to supply, plant, weed and protect young trees. link
Here’s a comprehensive list of all the Countryside Stewardship grants the government offer.
It’s also worth talking to the Woodland Trust, they have a whole section on Large Scale tree planting and the support they can provide includes: Tailored advice, Grants and funding & Trees and protection.