I would say it depends how much planting you are planning to do, but getting in touch with the Forestry Commission local officer is a good thing, whether or not you decide in the end to go for grants.
You don't need to pay somebody to write a plan for you - you can write it yourself. They will NOT tell you what to do, although they will point out elements of good practice. You can set the overall objectives of your plan - ours is for wildlife and use by community groups - they won't insist on your producing timber from the wood. The Sylva Foundation have a really neat tool for producing a woodland management plan on their
MyForest web site, including inventory, mapping and planning tools.
You WILL need to stick to the plan, but there are big advantages to having a plan - including the exemption from the felling limit and over-riding of existing tree protection orders - plus lots of advice and help if you want it.
We did not have a planting grant for planting to improve diversity within our existing 11 acre woodland, but when we bought 9 acres next to it, and wanted to plant it with woodland to link to another small piece of woodland, and a nature reserve owned by the Council/Wildlife Trust, then we had little choice, as we needed to plant about 5500 trees and couldn't afford that.
Talking to the FC officer doesn't oblige you to apply for a grant, but at least you can find out what help might be available. They are VERY keen to see good management of woodlands, and this can include leaving sections, or even the whole woodland alone, right up to commercial forestry. It is up to you. You lose nothing by asking.