There are a few approaches that might help you.
What's the area of your life that you're most dissatisfied with? Concentrate on that to begin with, and I know it might sound a bit simplistic, but work out a "where do I want to be in 5 years/3 years/18 months and how do I get there" plan. Does your uni have a coaching service you might be able to plug into? When I worked in academia for a bit a colleague was completing his coaching qualification and I was his coachee; it was so helpful especially with working out where I was stuck. In this case it was related to the job but the approaches I learned were so helpful for life in general. I also found listening to some of the Paul McKenna meditations really helped; one visualisation in particular basically asked you to look at your future life and what did you want it to look like.
Or, what do you enjoy doing the most? Either in your current job or outside work. What are your skills? Could you volunteer in something you're interested in (that is something that I believe some universities and big employers still support a few days a year - to be cynical, it helps them tick their "contributing to the community" quota).
Do you have anything creative you like to do? Drawing, writing, photography, singing, painting, knitting, crochet? Or physical - hiking, swimming, netball, salsa, cooking - anything really. Just something to stop work being the be-all and end-all. If you ask any nurse who's worked with the dying, they'll tell you that when it gets to the end of life, it's a rare person indeed who wishes they'd spent more time in the office...
On a separate note, I'm a bit curious about the comment up-thread about breaks for the civil service every five years though; as an ex-civil servant and NHS worker, I don't remember us being allowed sabbaticals every 5 years - unpaid career breaks, maybe, once or twice in a long career, with special dispensation from your manager and for a jolly good reason (health; study; visiting family in Australia; walking the Camino), but they usually used to come with conditions, like you couldn't work for anyone else during them...I think the "here, have a holiday every 5 years" days are long gone, like so much else. Unfortunately this also applies to career development loans, which I think were alluded to up-thread - www.findamasters.com/funding/guides/career-development-loans.aspx.
If you did want to do further study, you might get a bursary, your uni might offer subsidised training (not free), or there are a few countries that do offer masters courses with no tuition fees, including some online courses (a friend of mine did her masters in digital library studies this way, all they had to pay for was the study school in the country once a year for a couple of years) - have a look at www.mastersportal.com/countries/19/norway.html as an example.
In terms of finding a partner, if you still want to, have you tried online dating? It doesn't work for everyone, but there are three very happy marriages amongst my family and close friends that owe their existence to online sites. And I met previous partners via work, courses (writing) and hobbies (hospital radio), in general (though I did get chatting to one very nice, if short lived, partner at a bus stop, believe it or not). And though you feel you've missed out on your own children (as have I), people adopt or become step-parents at all stages of life.
Good luck, anyway.