Well I'm here to shine a light on this, sorry if I'm a bit late
But yes, you can make hay with an ATV/Quad, although in your case, I would certainly not recommend it! For the amount of hay you are making, and will be needing, you'd be better off renting a tractor/equipment, to make it with an ATV/Quad, it will be costing in access of 3000 quid.
The only quad accessories I would consider for smallholders in general, would be a Stock Trailer, Muck spreader, toppers, harrows, fertilizers and sprayers (Boom or spot).
Things like mowers, balers, rollers are all a waste of money (at least for the countries we live in!)