I've managed to sort out the tight spot on the drum, by backing off the adjusters, putting some emery cloth on top of one of the shoes then putting the drum back on and slowly winding the adjuster in a bit a time while spinning the drum. Took forever but seems to have worked.
Final question is on split pins with castellated nuts. Which way round is the 'right way' and why? Do you spread the legs of the pin around the nut, or along the shaft. I don't think it makes any difference so long as you have the right size split pin, but would be interested in opinions as it's something I've often wondered about.