50% over the limit is almost certainly a trip to the magistrates. Look very sorry, explain the situation but accept it was an error of judgement on your part and that you accept you are guilty. Even when you're in the right there is little point trying to argue as the police are all wearing shiny bright halos and ask motorist you are scum who needs to be made an example of.

My SP50 in 2012 made no difference at all to my insurance.