I reckon it might be something to do with going fixed and not changing chain at the same time as the sprocket (this also justifies the purchase of a half link chain - anywhere other than Hub Jub have these?). The noise is doing my nut - I pride myself on a quiet ride. Again, thanks for the input, we can continue the analysis with the offending bike present on Sunday's social ride.
I reckon it might be something to do with going fixed and not changing chain at the same time as the sprocket (this also justifies the purchase of a half link chain - anywhere other than Hub Jub have these?). The noise is doing my nut - I pride myself on a quiet ride. Again, thanks for the input, we can continue the analysis with the offending bike present on Sunday's social ride.