The Ridea front derailleur clamp was delivered today so I did an trial fit of the clamp and the Shimano FD-5700 derailleur. This revealed that the chainrings need to be moved out by several millimetres to be within the range of derailleur cage movement. Close scrutiny of the bottom bracket area revealed that there are spacers (2mm + 0.5mm?) on the non-drive size where the BB screws into the frame. If they can be moved to the drive side then that should shift the cranks across by 2.5mm which might just be sufficient. However, to try that shift that I'll have to get an external BB tool. I don't think my feet will notice the lateral shift in the cranks.