Thank youProbably best place to start is..... dig a hole (with a spade) to see if you can see how the soil feels and looks - is there a compacted zone? If there is then consider a pasture lifter to break compacted layer but only do when the soil is fairly dry and not saturated. If you did need to use a lifter drive it across the slope, not up and down. (This digging hole step is the bit that can tell you a lot before you start jumping around looking at solutions).
Then take care of stocking rates depending on grass availability and soil moisture - to not overgraze and stop poaching.
Well rotted farmyard manure (stuff that's heated up well to kill weed seeds) would also help with organic matter and nutrients to compliment what your soil analysis is telling you about fertiliser needs.
Once you've got the soil structure sorted and soil nutrient at the optimum levels then could consider stitching in new grass seed. Herbal leys have good potential to compete out weeds too, but that's another topic.....
Two ideas on top to add:A picture of the issue. Not too bothered by some thistles, but concerned about the state of the soil with heave and erosion. Thank you everyone for your thoughts.