I hope this works, and the users who previously commented on this thread can read this:
Firstly, huge thanks to Ian for providing a link to the photographs, and for Steven for posting them.
I'm currently refurbishing a Thornton Pickard Junior Special Ruby Reflex - the variant which has a 120 roll film back. Thanks to the information above, and some generous help, I have managed to get the shutter out of the camera. Unfortunately for me, one set of tapes have decayed to such an extent that it is no longer possible to ascertain their original length. However, the second blind is in tact. Is it safe for me to assume both sets of tapes were the same length? Secondly, does anyone know a source for shutter blind material? I am found some black fabric which is used in the manufacture of vertical blinds. This is the correct thickness, and is light light, but unfortunately is 6mm short of the correct width. Finally, when I come to reassemble the shutter blinds am I correct in assuming they are both set to the same tension (i.e. x number of turns on the take-up blind), therefore the exposure is governed not by variation of speed of travel, but by variation in the width of the slit which is effected by the two blinds operating in unison?