your previous record will only be brought up for consideration when sentencing, so only if you plead guilty or are found guilty. I doubt a big deal would be made of it as it is unrelated, but it is within a reasonably short amount of time so the prosecution would probably bring it up.
I assume you know that if you plead guilty, you get an automatic reduction in any sentence (fine, community punishment, etc), and the earlier you enter your plea the greater reduction you get, up to a third.
look at the wording on the summons. if you're guilty of what it alleges I would suggest you plead guilty. your solicitor probably knows best but it is for you to decide...