Just to clarify: the first ac (as I arrived) joined correctly over the upwind numbers. As he was lower than me and on my right, he had right of way although I still think it was poor airmanship.
The second (as I departed) was well upwind of the numbers - the airfield in question doesn't have a long runway, the wind was light, and so we didn't reach circuit height (1000ft) until some way upwind. Given that and his position when we saw him (to the right and flying level) I very much doubt he was at the end of a deadside descent. Again he was on my right, so had right of way.
And the answer to a RH circuit is of course to keep the airfield on the RIGHT while joining - but of course you all knew that, didn't you...
Tim