Thought I had blown this one too. Today, I flushed one out of a ditch at Myers Farm near Potton. I must have visited this site 20+ times at dawn and dusk looking for them, so can only assume that this one was on migration. Saw it well in flight, then it started to scold me from the dense herbage.
So following CS and YG at Tetworth on Saturday and GH today, I am now on 128 self-found, zero-carbon (136 total) - the only list that really matters to me. Game on Messrs Bashford and Grimsey (although I suspect Mr Lynch will be right in the mix when he updates his total).
Tetworth is sure to score me some ticks this autumn...