Those who had secured a U.K. university place (a much smaller section of the population in those days) could opt to defer their National Service until after they had graduated - although many preferred to do it first and 'get it out of the way'. Medical students had an indefinite deferment which amounted to exemption. There was much less 'dodging the column' in the National Service era anyway - partly because there was no major war on for most of it, partly because there was still a cultural expectation that you would do it, most of their parents had had to do their bit in WW2 and didn't see why you shouldn't have to go as well. The draft ended before that Sixties counter culture got going.

My late father had a lifelong dislike for Colin Cowdrey, perceiving him to have got out of National Service by playing cricket. He wasn't the only one who took that view.