I think it will be possible but I doubt he would be looking at entry into a top uni. Most of the courses will still require 300+ ucas points because they are designed for people who did the wrong subjects. However some decent unis will be asking for 120-180 ucas points. If he aims for these universities, emails the department showing his interest and writes a decent personal statement I honestly can't see him being refused entry. Only problem is I think most will require GCSE English and Maths at C or above though.