talk to a lawyer, not a load of guessers on a website 
think people like white daltons will give a little free advice on whether its worth fighting over the phone
with regard to the letter from mcn, here is the way i read that issue.
if you get charged with anything they read you your rights, you know the bit about remainind silent etc, as in this case you have not been afforded such a right any thing you say to them is therefore inadmissable evidence.
There is also a time limit where they have to disclose all the evidence to the accused otherwise it is not admisable in an English court.
What evidence have they shown you?
all is not lost, fight it.