The flocks' flight directions reported from Dorset headlands and South East Devon is strongly westerly. The directions at Soar and Prawle is South/Southeast. I think birds are crossing the channel, coasting west to the south Devon coast then re-orientating South/Southeast to recross the channel. This idea is supported by the fact that no mass movements have been reported in Cornwall. Further east along the coast no mass movements were reported in Kent or Sussex so birds could be crossing from France between Devon and Sussex.
Very few Continental birds have been seen crossing the North Sea (very few ringing recoveries) and few flocks seen over oil rigs.