Just before turning in for the night (we had a 04.30 alarm set this morning), I checked 50MHz again and CW was buzzing! Lots of I, SM coming in. But to my enormous surprise, I could hear a number of US stations taking part in their VHF contest. The first station I heard was NN1N, who astonished me by coming straight back to a very tentative call. The other stations I heard had big pileups and I didn't get involved, but it was particularly good to hear the Mt Greylock Expeditionary Force, W2SZ coming through. There was a very loud K1 who had an enormous pileup.
No doubt for those with a bigger aerial than a vertical, there was some really great DX to be had, but I was quite satisfied with my transatlantic QSO.