Speeding Ticket in Ireland

I visited Ireland in July 2015, and had a great trip.  About a month later a received a speeding ticket that included a photo of the license plate for my rental car, a location and no further documentation of the offense.  I was provided with instructions to complete a Fixed Charge Form and to submit 80 Euros.  The instructions indicated that if I did not submit this material by late in September 2015 the charges would double, and then keep doubling there after.  The material appeared to come from an authentic government agency, however I had read about speeding ticket scams.  Additionally I have never had a speeding ticket, and I took great care to follow signage while driving in Ireland; you never know when a pedestrian or sheep might be around the bend.  So instead of sending a credit card, I send a Bank Draft, which cost me, and I mailed the material 3 weeks before the deadline via Priority Mail, for rapid delivery.  All the mail I received from the Irish Fixed Charge Processing Office via snail delivery required only 4-5 days to reach me in the US.  Because I was skeptical that this entire exercise was really aimed at revenue enhancement versus true traffic enforcement, and I was concerned about reports of scams, I photographed all the material I sent, and in its envelope, and the priority mailing packet.A month later I received my Bank Draft back, a claim that the material arrived after the 28 day deadline, and a request for double the fine.  Additionally the Fixed Charge Office claimed they had not received the required documentation.  This appears to be a scam operated by a government.  I really wish, if revenue is needed, that a user fee had been added to the rental charge.  Much less aggravation and much less of a tarnish on an other wise nice trip and travel venue.