Definitely not cuddly caterpillars!
Those yellow and black bands really do mean keep off!
These are lovely cinnabar moth caterpillars. They live on ragwort- it's the only thing they eat- here growing in the Crow Wood CIC orchard- which contains some excitingly poisonous alkaloids. The caterpillars keep the alkaloids in their body, making them poisonous to predators. Also, the spikes will give you a nasty rash (never touch a furry caterpillar!).
We were so pleased to see cinnabar moths on the allotment earlier this year- it's great that we should get another generation of them growing in their chrysalises soon!