Hiya Lisalisa,
I remember the thread from the first time you posted on this subject. And let me preface this post with the fact that I am no lawyer, so there are definitely others here who are more qualified than I am to advise. But, I'm not one to keep to myself, so here are my thoughts.
You are concerned abour the possibility of alerting the senior partners to the situation and hence expediting the possibility of redundancy. My first reaction is to question whether they don't already know about it. It's been going on for some time. I would think it's probably known to them already. If you contact them, they can see that you are being proactive. If you don't contact them, you risk having them know about the situation but not knowing that you are doing anything about it.
Also, you mention that you deleted earlier e-mails on this subject. Do you have any evidence that might show you expressed these concerns before more junior staff were hired. That might be a handy piece of evidence to demonstrate that the firm should not have hired the junior staff, and hence would not be justified in letting you go.
Also, re the sexual harrassment comments. I completely understand you not wanting to toot that phrase, but I wonder if their practices conflict with flexible working rights (which is of course not specific to women -- well, not in theory although it might be in practice).