Hi,
If you catch it before it starts to go to seed, there are a couple of specialist killers for Ragwort, the one we sell & Use is "Barrier H" - this is the blurb on it :
"Fully licensed, environmentally friendly, agricultural herbicide that destroys ragwort in record time.
Ideal to use all year round - not affected by frost. Sold as a ready to use spot spray in a 5 litre container with applicator gun. Keep animals off treated areas for two weeks or until the plant is completely dead and any remaining debris removed. Always read the label. Use pesticides safely. MAPP: 10136. "
Not cheap, but then weekillers generally aren't
Thanks