Given that there would be no instructors available, nowhere to train conscripts, little for them to do that would be worth the cost and effort - and the fact that the UK's Armed Forces are already patched up with reservists of one form or other, the chances of conscription ever being reintroduced in the UK are less than zero.
National Service was being would down from 1957 and the last conscripts were called up in 1960.
Think about how much bigger the UK's Armed Forces were then - and how many more aerodromes, barracks and ships we had, compared to today's pitiful state.