Oh no, zippi (and sunnyjim)... I love mature students. They add so much to any group, and just read and understand things in a different way, not to mention actually giving a shit, which is not always the case with the 18 year olds, bless 'em!
Sunnyjim... I don't know if this is possible (don't know the subject at all) but could you do an essay in which in the first half you show that you have read and digested the course material ('Joe Bloggs (out-of-date article: 1999) argues that blah blah blah is the case, because x, y and z...') and then in the second half you show some alternative points of view ('Bloggs' point of view has more recently been questioned by Someone, who points out that a, b and c'). That way, you show that you've done what my PhD supervisor used to call 'being a good girl' (i.e. citing all the people you are SUPPOSED to cite in these cases regardless of what you think of them) but you also show that you can think for yourself. Then, if you feel that you have been marked down for thinking for yourself, ask for the TMA to be re-marked. A certain proportion of essays will be second-marked anyway, but if you specifically ask for this to happen they should do it.
Oh, and obviously (just to echo everyone else) don't buy an essay! (If you get found out, which is eminently feasible, you will never get accepted to do a PhD, so you have a lot to lose.)
Good luck.