Actually finally making progress on the Sunbeam restoration. Having looked at pics of similar Sunbeams (there's a cracker on eBay at the moment that looks identical, but prefectly restored (i.e. not home lug-lined like mine) that's up for sale at an astronomical £650) I've realised the headset that came off (and was mislaid by persons who I'm still annoyed at) is of the 'headclip' variety.
Essentially the stem doesn't have an expanding bolt, but is instead held in place by a clamp that goes round the steerer tube and tightens, the steerer tube having a slot in it that means it can be contracted.
Headlcips seem to be rarer than hen's teeth (I have chickens, I can verify), though some do occasionally come up for sale (though I'm not buying a Chater Lea, they sell for £150 a time), and I'm keeping an eye out. But in the meantime, and before I can try a raid on the Bike Station's parts bins, I thought I'd see if anyone on CCE just happened to have one kicking about (I do believe I'm looking at bike hoarders extraordinaire chdot and LaidBack in the main here).
My 'bodge' option involves heavy duty jubilee clipping, which should work.
2-3 weeks I'm finally going to have this on the road again.