Sorry [member=212273]Freshair_Dave[/member], we all missed your post when you posted it for some reason. (Sometimes the forum software doesn't seem to show new posts under "Unread", not sure why.)
You need entitlements for your land in order to register for and claim payments. You will need to buy the entitlements once you have sufficient land. I am not sure how the market for entitlements is working now, since Brexit, as I think no-one is yet sure what will be the future of subsidies now that they won't be coming from the EU. Your local land agent will be able to advise.
Once you are registered, you would have access to any grants and so on. I have not farmed in Wales and I do not know if the schemes differ to England. I am also out of date with the situation in England, having moved from an upland farm in Cumbria to a Cornish smallholding nearly 5 years ago. We have chosen to not register for subsidies here, although we have sufficient ground (approx 15 of our 32 acres is eligible), because the paperwork is an utter nightmare, with so little land there is no way the payments would cover an agent to do the paperwork, the limitations imposed would far outweigh any tiny income, not to mention the increased likelihood of inspections and all the work and disruption that that entails.
In England (with the proviso there could have been changes in the last 5 years), no, woodland is not eligible. And there are no subsidies for fencing with the exception that there may be some assistance if establishing new native woodland, where that is regarded as beneficial by your local Natural England ecologist and he/she thinks it needs fencing from your own livestock and or from deer, and can find a scheme for you to use. (And note that the land so planted would then become ineligible for farming subsidies.) In any case, I don't think renewal of existing fencing would ever be covered.
You may well find that a local shepherd would take the land for grazing, and be happy to either use electric to augment your existing fencing or possibly to undertake repairs to / renewal of fencing as part of the arrangement. You would make far more money out of letting the grazing than trying to farm it yourself. No idea what grazing might fetch where you are, but in Cumbria we used to pay £100/acre for summer grazing (fenced) and a little less for 11-months' grazing with responsibility for maintaining the fencing.
Most farmers barely make a living from their land; the average farmer's income is a little over £8,000 pa after expenses. (The subsidies basically make it feasible to farm at a loss.) Almost all farms have to diversify (often tourism) and / or have someone bring in additional income. The farmer I lived with in Cumbria did make a living out of his 300-ish acres, but was on a Higher-level Environmental Scheme to do so. The livestock made a loss. And the Northumberland moorland farm I was on before that also made a decent income from its 1,000+ acres - but again, with the Higher-level Environmental Scheme compensating for the net cost of farming livestock in order to manage the moorland.