After I took into account pad face wear (doing the worn ones, by feel, comparing it to known good gaps), I eliminated tappet noise.
Some time after I noticed the first 6 or 7 rockers (front half on engine, furthest away from oil feed into shaft at rear) weren't dribbling oil from top holes at idle. stripped down rockers and the oil holes were clear, though shaft very worn at front of shaft, progressing along it to rear.
New shaft sorted the oil feed. Didn't appear to make any difference to noise (where the area of wear is on shaft, corresponds to where the load/pressure is on shaft/rockers due to the valve springs I think?, so maybe this also doesn't make it noisy/rattly with wear?. .
I used my old rockers, as apparently the shaft wears more and new rockers may not be good quality, as isn't, probably the new shaft (£25.00), Better ones may be available for around £75.00, Chris witter I think supplies them, though maybe others?.
Dave