Over the last few months my bounce rate has increased massively, almost doubled. Seems to be caused by long tail giving me inappropriate traffic.
My main 2 word term which has had my page at #1 for the last 13 years (with notable exceptions) has dropped to #3. I notice that, subjectively, the sites that have moved above me, would probably have their "Keyword Significance" as reported by WMT more towards one of the two words than my own site. For example if the term was <<widget fettling>> my site is more about fettling, those that have moved above are more about widgets.
If I search for the single word <<widget>> my home page has dropped from about #30 to #86. I used to be the first widget fettling site listed in SERPS for the widget, now I'm the fourth.
If I search for <fettling>> with pages from the UK selected I've dropped from #90 to #199.
Still far more questions raised than answers found.