This is mainly a note for future reference for myself, since I always seem to have an ABSOLUTE F*CKING NIGHTMARE trying to get Subclipse working on any new install of Eclipse. Thankfully it seems to have got better in the last few months now that Eclipse automatically finds dependencies, and you don't have to realise that Subclipse requires Buckminster, Buckminster requires ECF, and ECF requires Equinox until YOUR HEAD EXPLODES.
Anyway, now all it seems you have to do is select the Tigris update site as per here and select all the Subclipse components.
Then finally, for the magic step that makes it all work that took me about 3 hours searching the internet for, you have to right-click on your project and select Team -> Share.
(Why it couldn't realise that a project is already in subversion by seeing if there were any .svn directories is something I can't answer. There may be good reasons for this).