As already mentioned it should be changed every 60k or 4 years, which ever comes soonest. On that basis it should have been done in 2010
I'd get it changed asap to be honest, I'm doing mine this weekend...car has only done 68k but it'll be it's 3rd cambelt change (done in 2005, 2009 and now 2013).
You could run it to the ground and then shell out of another car to run into the ground but at £600 a time that'll be a false economy. In my opinion you're better spending on it now and running it for longer, happy in the knowledge that it's been done.