Thanks very much for suggestions.

I rang the place in my link and they said that the glue is not suitable as it would probably come out in the wash, but to use a patch of poly material supplied by them and sew on with invisable thread.

I bought a 0.5m square of polyautherne material from them (white a pity it wasn't availabe n skin colour) cut a patch to fit front of piece that was frayed sewed it on with the invisable thread (as its hard to see put something black on table where you are working so it shows up easily) and it seems to have done the job.

0.5m square of white poly material (takes tape fine) cost me £15.60 about $22.