Bristly Oxtongue (Picris echioides)
At first glance this might look like another of those hard to identify Dandelion 'look-a-likes' but actually it is really easy to pick out because its leaves are prickly (a bit like a thistle) but the main feature is the presence of 'bumps' all over the leaves, they look a bit like galls. This is a difficult to describe and illustrate feature but once you find the plant you will know what I mean, it is like no other.
The flower head turns in to the classic Dandelion clock when it is over and the same plant produces many stems each with flowers at various stages in the cycle. You will find new buds, full flowers like this one and some with seed heads all on the same plant.
A scruffy plant yes, but these yellow complex flower heads are quite delightful and are a prime nectar source for insects late in the year, particularly for bees and hoverflies.