Hmm for an all english semi-final to happen it would require that no english team draw each other for the quarterfinals and there is only about 0.95% chance of that happening. 
4!/(choose(8,2)*choose(6,2)*choose(4,2)*choose(2,2))=0.0095

4!/(choose(8,2)*choose(6,2)*choose(4,2)*choose(2,2))=0.0095