Does this mean that he doesn't have to have a retrial?
The prosecution are appealing the decision, so it's not a definite yet. If the appeal fails (that is if the appeal court agree with the trial judge) then unless there is a further successful appeal to SCOTUK, there will be no trial.
The TL;DR is that the prosecution have fucked up big time. Which isn't that unusual. What is unusual is that they had a second chance and fucked that up too. Which even in England is a bit too much.
Given how carefully prosecutions are stacked against the defendant when it comes to shonky evidence, for a judge (of all people) to throw a case out based on it is some weapons-grade fuckups.
But no one will be sacked, if that's what you are worried about.
It's hard being a lawyer with this level of incompetence around.