Mornin' all

Another question - being an outside in all weathers car, the cotton thread in the hood started turning a light shade of green. BHM kindly cleaned this when car was with them post side screen repairs, and advise treating the thread every three months or so.

Does anyone have experience of a suitable preservative / cleaner please? Option suggested so far are furniture wax or silicon fabric treatment, as per http://www.grangers.co.uk/productview.asp?id=24

Many thanks