As L&M says. Often all that's needed is a couple of years of close-cropping by sheep, plus their generous donations of muck. The close-cropping causes tillering of the grass ie lots of stalks grow from each plant, rather than the few which grow if the grass gets too long without grazing or rolling. Artificial fertilisers tend to prevent clover from growing/thriving - this is a natural adder of nitrogen, so you might find benefit to your overall pasture quality of seeding any bare or mossy patches with white clover seed. Clover takes a couple of years to establish itself but doesn't seem to mind being grazed during this time.
Ploughing and re-seeding, as well as being expensive and leaving you nowhere to run your stock while the grass establishes itself, will destroy any native and deep rooted plants which help bring minerals to the surface roots of grass from deep below. These plants also make much better grazing for many stock than the quick-grown, fertiliser supported monograsses. To mimic this natural variety of plants in your grazing you would need to use some very expensive seed.
On such a small acreage, hand weeding of thistles, nettles, dockens etc is not too much work and saves using weedkillers.