Hi Perrywinkle,
It's not a bad idea. What you should do is contact your salaries section in the public body and get them to estimate (for instance) what 55 Euro per week will allow you to buy back. You can buy in block as well, but that it more expensive (although it's a once-off cost)
Very roughly, (although it does depend on age!), one years service is around 1% per annum of your gross wage. But the good folks of salaries should be able to help you out on this one.
As for the pension, I think it's the best in town - 1/80 for each year worked up plus 3/80 per year added to a gratuity, for relatively speaking a small amount. If you don't need the money from the pension you're getting, I'd start buying back years and fund it from extra deductions from your pay packet.
Let us know how you get on.
Regards,
OpusnBill