Lark?

We were at Cadgwith Cove in Cornwall this afternoon, sitting on the cliff top overlooking the village. Several times we saw what looked like a lark rising from the shrubbery growing along the cliff face. The bird looked smaller than a Skylark, and its song did not seem as mellow or tuneful and varied as a Skylark. It rose, while singing, to just above level with the cliff top, but instead of hovering there, it flicked its tail vertical and drifted back down into the shrubbery. Because the bird was about level with our eyeline, it was quite clear that its tail was held vertical (like a wren) during the descent - I don't know if Skylarks do that because I've only seen them from below. So in summary, its behaviour was like an understated Skylark, rising while singing, then drifting silently down into the shrubbery again. I would have identified it as a shore lark, but my trusty bird book shows them only on the east coast of the UK and only in winter. Anyone have any idea what our bird might have been?