Grass enrichment to me means getting a richer species mix, especially encouraging clover. Beware of piling on the nitrogen in chemical form as it encourages rapid lush growth of certain grass species, which can lead to grass staggers and scouring in your sheep. It actively discourages both clover growth, and a mix of native grazing species. Allowing your grass to develop over a few years, from rotational pasture to permanent pasture can be scary if you don't have confidence in what you are doing, but it makes for healthy sheep.
Our grass looks rubbish at the moment, because it's had heavy snow lying on it for ages, and severe frosts over the winter. It has almost no nutritive value. Compared to our neighbours who will be out there with the fertiliser spreaders any day, our grass will start to grow a bit later, and more slowly than theirs, but ultimately it will be a darker green and much more palatable to the sheep and full of a variety of nutrients. We feed good hay over the winter, maybe for a bit longer than our neighbours, but we can do that as we are hobby farmers, whereas they are running a business.
To get more species rich grazing, buy an organic seed mix specifically for grazing animals. There are various ways to add it to your pasture such as slit sowing, where you make a series of slits into the sward then sprinkle your seeds in, or find some bare patches, scuff up the surface and sow your seed there. You can buy small plants which would establish well, but even for just 2 acres, planting them out would be a big job, and the cost would be much higher than seed.
However, you could be worrying about nothing and once the weather has warmed up and soil temps are 7C or higher, you might find you have some lovely grazing after all.