Hi den:
I understand your concern about the points on your licence, I believe that for this offence you could get 3-9 points which would of course disqualify you if more than 3.
Nevertheless, it's not automatic that you would get points, although it's likely, you may just get a fine.
I'd advise you to plead guilty because the Court's more likely to respect your honesty rather than have someone plead not guilty only to be then convicted. I say that because from what you describe it seems as if you're "banged to rights."
Besides, it's more than possible that you may not be ultimately disqualified anyway if you can show the Court that by doing so would cause you hardship because of the fact that your livelihood depends on you having your licence.
Good luck.