I was just watching my hero, serena williams come from a set down to win the semis of the miami open in tough three sets. She is thru to the final on sat were she is garanteed at least some hard core cash.

Then there is me, looking forward to starting a four yr PhD, during which time I will earn £1200.
Will my life be comfortable after 4yrs of study?

I would say that after a certain point the "law of diminishing returns" kicks in. Upto first degree level I reckon that continued education is linked with increased potential earnings for every step you take, so someone with only GCSEs generally has a significantly lower earning potential than someone with A levels (and a similar jump between A levels and Degree).

However, after this point the premium is not as high between say BSc and MSc(unless you are in a field that demands a postgraduate qualification). Likewise that second masters is probably not going to earn you much more.

Many think a PhD can actually harm your earnings, because a) you never recover from the debt you accrue while you could be earning b) you may be considered "over-educated" and repeatedly overlooked from some jobs.