Be realistic because exceptions just don't happen: if applying to Big 4 you will be competing against people with good degrees (2:1 or better) from leading universities at grad level, and against grads from same with directly relevant expertise and experience with big firms at more senior levels; if MBB you will be competing against oxbridge etc and the creme de la creme of the grads of the year, and experienced hires with truly exceptional experience, and many of the experienced hires at whatever firm will have come from other consulting firms. In many cases experienced hires will be MBA qualified. Among all this competition you will have no degree, no relevant experience, no way of demonstrating the analytical rigour required, and no networks. Partners and Senior Managers sell consulting projects - and we are talking multi-Million £££ here. It just won't happen as it is; if you are serious about getting into consultancy go and get a degree and - assumuming your A levels are good - you may be able to get in. If you can't or won't do the work, you won't ever make it.