Use of field?

Unfortunately, he refuses to maintain his fencing and I have had to put up a stock-proof fence  at my own expense. I can cope with the sheep eating my flowers but worry that eventually the cattle will damage the fence.

I could be wrong but I think it's legally his problem to keep his stock under control and he is responsible for damages. On the other hand.. a) he's a farmer & b) you don't want to go to war with a neighbour in the country. Been there!

You don't say where you are or what the land is like - assuming it's good pasture because he keeps cattle on it (that need better land than sheep). A lot depends on you yourself - do you want a business or just to make some good use of the land?

You could use it to grow hay and get a farmer to cut and bale or make haylage.
You could set up an organic poultry enterprise - perhaps geese or turkeys but that's livestock. Incidentally you can get a franchise on free-range chickens. Almost a turn-key operation but you'd need at least £350,000 in available finance!!!
A tree nursery.. Christmas trees
Split into allotments and rent out.
Rent it out to a farmer or go into a joint venture with a farmer who ethically agrees with you.
Llamas or Alpacas
Offer the land for use by an animal rescue with horses needing land

Hope that sparks some ideas for you

Thank you both for your very helpful replies. I suppose what I want would be some income from the field but minimal work (don't we all?!) as I don't really have the time. This IS a very "horsey" area so I will ask around about what I might earn just renting it out  to horse owners (there ARE responsible ones around here who clearly care for their animals).
Llamas WOULD be nice, though...
Thanks again

Ahem.  As a conservation adviser, I would advise cutting for hay.  The reason is that it's the best way of seeing what your land is like whilst keeping your options open for a future change of plan.  Cut after mid-July to see the best range of wildflowers.  See if you get different sorts in different parts of the field which will give you a clue as to different soil types and conditions.  If you get a lot of thistles, ragwort or docks cut earlier before they flower and set seed, they are covered by the Weeds Act and you are required to stop their spread onto neighbouring farmland.

Planting native woodland is an option I don't think has been suggested.  It's a long term investment, but you could end up with valuable products if you go for things like hazel, sweet chestnut (OK not exactly native), ash, oak, holly.  I think I would look seriously at that unless the hay meadow experiment turns up really nice species rich grassland.  I can see myself pottering around making hurdles in ten years time.  You could get the local community involved too.

Leaving it "fallow" for wildlife is not something we actually ask for in large quantities, more in strips and small patches targetted along rivers.  Things which take advantage of that sort of habitat are fairly common and adpatable, whereas your species rich hay meadows and native woodlands support more specialised rarities.

Also look at the surrounding areas to see what is possible and what linkages you could make for wildlife.

Again, thanks to everyone. Seen a local lawyer who advised going for it as it would increase the value of my house having six acres attached. I would LOVE it to be some sort of wildlife haven but not sure if that is feasible or not. I am REALLY new to this and very green - in both senses of the word! - so all your advice and suggestions are much appreciated. Probably should have mentioned that raising animals for slaughter is not an option for me as I'm a veggie...