Hi paddy:
Sorry to hear of your unfortunate experience. Most of us have "been there" at one time or another.
Anyway, the offence can carry a fine plus between 3-9 penalty points.
I'd seek urgent legal advice - why not contact your local Citizens Advice Bureau - they can provide free advice.
Attending the Police Station for interview, although daunting, is not as terrible as it seems. The Police are not "out to get you", they have a job to do to gather evidence and information and you would be well advised to attend. If not, you could find yourself being arrested and taken there.
During the interview you would be verbally cautioned, meaning you have the choice to answer questions or not, you will be advised that you are not under arrest and are free to leave at any time, however as I've already stated, my guess is that if you wanted to do so you'd probably be arrested and detained anyway, hence a cache 22 situation.
At the end of the interview you'd be advised as to what else will happen, i.e. you may be reported for summons for an offence. And in all probability you'd have your antecedents(fingerprints, DNA etc)taken. Apart from that, not a lot!
Hope this helps. Good luck.