Its not possible to make a 'decent income' from a small woodland just from the timber that grows there. If for example you maximised the amount of firewood you could sustainably grow and sell on 4.5 acres, it might produce something like £2000 a year, a return of maybe 3% per annum on your investment. Likewise, to grow big trees to sell for timber is a very long term project, the likes of oak taking a Century to mature, so if planting for future timber harvests, you're unlikely to see the benefits yourself.
Where there is a very real possibility of a 'decent income' is paying activities that are held in the wood that people will pay for. Traditionally one of the most lucrative has been pheasant rearing and charging 'the sporting fraternity' to come and blast the poor beasts into oblivion. More recently there has been a growing demand for people to do woodland activities such as crafts, bushcraft, LARP (paintball etc) and glamping. That could yield a reasonable income and we get frequent requests on the forum from people wanting a wood to hire to pursue that ambition. Quite how much you can earn will depend on how good you are at the proposed activity and marketing yourself. I dare say Ray Mears or Bear Grills could make £500,000 a year on 4 acres by charging people £1000 each for a weekends instruction is catching rabbits or surviving on acorns. A very successful craft tutor, Guy Mallinson, seems to have a very well thought through operation near us, where people pay surprisingly large amounts to stay on sight glamping and make a spoon or whatever, but he seems very slick at having a nice setup and marketing it.
I am perhaps in a similar position to yourself, but have landed on my feet more by accident than design. As a craftsman for over 30 years, I can make things and exist happily on a modest income. I'm also a bit of a dreamer, good salesman, and come up with all manner of ideas, some of which are viable, others fall by the wayside, but I've never let cynics stop me from trying them out. What I didn't realise when I bought my small wood is quite what was 'under the surface'. I've accidentally acquired several hundred tons of prime Oak ready for thinning, and an unlimited amount of lovely clay on a historically important clay extraction site. (Useful when you're a potter !). I'm turning my hand to making stuff from the Oak, planking & selling the surplus timber, and if needs be reviving the making of the style of pots that were made locally from the very same clay in my wood. I have good access and the opportunity for a decent parking area and simple building, so I can use the wood as a venue for working in, exhibitions of my wares or basecamp for activities such as pottery workshops. It also helps a huge amount to have the right personal circumstances; I have no debt, savings, good health and a wife who feeds me with a regular job.
You need to think a bit outside of the box too, a building will be unlikely to get planning consent, but nobody can stop you doing stuff in the open air under canvass- which also feels more appealing. Basic stuff like parking space is important. Insurance is not expensive, basic liability packages might cost something like £150, more if you're teaching people to throw axes or climb trees.
Yes, I think you can go for it with the right attitude, determination, and maybe a bit of luck. By posting on this forum you've maybe already taken that first important step- thinking about doing it. There are people who achieve their plans and dreams, others who due to needing to pay the mortgage and feed the kids tolerate rather more tedious 'regular' existences. If you don't try, you'll never find out whether it'll work, its largely down to you. The important things to look for are the location of the wood, access, anything that impacts on it like restrictive covenants or neighbours, eye appeal, nature of the trees, cost, distance to get there, budget needed for all the kit you'll need. Go for it.
