How much better are the UK barsfor my year at getting you to lean forward a bit?
Firstly, you're aware the actual 97-1871 "UK bars" are nothing like what's drawn in the '67 parts book?
If not, the actual shape and dimensions are at http://www.britcycle.com/Products/Handlebars/97_1871.htm
I tried the similar disc-brake version years ago on my T160 - horrible things, made me feel like my arms ought to come out of the middle of my chest.
Also I found the standard footrest position doesn't work with low 'bars - feet too far forward, exacerbated if you're tall; I'm not but I still have rearsets on the T160 with flat 'bars (Norman Hyde "M bars").
If you aren't aware of it, BCS has a webpage with links to dimensioned images of handlebars - http://www.britcycle.com/Products/Handlebars/handlebars.htm
I've 97-1870-type 'bars on my T100 but it doesn't use the screws-mounted horn/dipswitch so I was able to shorten each end, reducing the overall width, which makes them easier to live with.
would have to buy new cables I suppose.
Uh-uh, just route each existing cable around the front of the frame steering head; I always use "US"-length cables, routed this way with flatter 'bars.
wonder if the oil in frame ones are the same?
Yes and no. Later numbers were originally for 'no switch screw holes' and slightly longer for disc brake master cylinder. Unfortunately, a numpty at one of the wholesalers, tasked with reducing the number of parts, picked the drum-brake 26" width ...
So the only difference now is whether the 'bars have switch holes or not, disc-brake, the twistgrip sticks out beyond the end of the 'bar
but I appreciate that isn't an issue on a '67.