Thanks Stuart, I have in fact done just as suggested, and sent off a small order to Ost2rad, the spring was included and arrived by DHL today.
Have had some ‘fun’ with the handlebar yolk too. Someone had decided to lock the steering adjustment nut with the second nut, and fit the yolk on top, finishing off with the bolt that expands the clamping cone bearing down on a rubber washer, as the yolk would not go down any further than this image shows:
Rubber washer absent in this shot. Just one of a number of ‘oddities’ that previous owners have had a hand in.
All new cables have made such a difference too. It’s coming together.