I developed another roll of film last Sunday, with careful loading this time, and the number of 'lost' frames has drastically reduced.
From 6-8 earlier, now it's down to 3-4 and I'm counting smallish dots on the sprocket which would never print/scan.
Matt, Bill: I still couldn't use the clip (small changing bag maybe?) but a slow, even paced reeling seems to work better. The worst affected image was at the end of the roll which had firmly stuck to the layer below.
Thank you all once again for the spot-on analysis!