“... the way the court should consider the matter was to consider the relevant conduct of the parties, to consider prejudice and to consider whether there is any indication of harassment or other matters. In short, it seems to me that it is right that the court should look at the circumstances in which the discontinuance took place; but the court is also entitled to look at the position in the round, to have regard to the interests of justice and also to have regard to the not unimportant factor of the proper use of court resources.”