3 things really.
1) It's easy to pick on the professions from a government's viewpoint - the relative freedoms of professionalision means that you can proportion blame to another governing set of people. Also people mistrust those who have a body of knowledge so specialised they cannot have access to significant amounts of it without acceptance into the profession. Magician's circle anyone?
2) It's not the govt's duty to ensure more working class people do medicine, its duty is to ensure that people from all backgrounds are able to have a fair crack at getting onto a degree course that they want to do. Right now, it's not managed it, cos it scrapped/disencourages a vehicle of social mobility (Grammar schools - doctrinally wrong with Labour but probably necessary as an intermediary step to improving education) and has not replaced it with anything better.
3) And yes, the middle classes have it slightly easier in the medical applications, the parents are probably more occupied with the wellbeing of their children - fewer stresses of life given a better financial situation and able to provide more in supporting their child in getting the necessary work exp etc.... esp. when you have family or friends in the profession. People don't have to worry about the cost of visiting a particular uni, the extra cost of living in a more expensive area - limiting options to where to apply, guilt of financial sacrifices that may be necessary to go to university.
Better schools also have more experience and time (smaller year sizes/application co-ordinatorupil ratio in grammars and private schools) to help their students. In the end, it makes for pretty press coverage when the results come out for them. Also, they know more of the facts of medical applications and are not swamped by the tripe mountain of myth and spin counjoured up from years of accidental misinformation/anecdotes which has been given a special boost by the companies exploiting the situation and promising to "tell you all you ever need" (paraphrased) to guarentee you a place in medicine.
@ Holsy - if you can ever get enough people to organise a free fair conference for potential medics - i would doff my metaphorical hat to you. (and supply you with free drinks for life.)*
*Offer not guarenteed.
100s of personal statements examples here