Did part of my apprenticeship in the loom shop at Hurn.
Green string was used on BAC 1-11 wiring, however the Concorde wiring used different colours to identify the systems the wiring related to.
ISTR the spacing of ties was 6 ins on the 1-11 but 18 ins on Concorde to save weight.
When various looms are bundled together on the aircraft the string ties don't cause a rubbing issue whereas tie-wraps do.
When the looms were installed in the trunking in the roof of the baggage bays of the 1-11, plastic coated metal straps were used alternating with plastic tie-wraps.
Hope this helps.
P.S. The green waxed string was very good in the garden for peas and runner beans. (I still have some!)