No you don't have a case for either unfair dismissal or age discrimination - a company is not compelled to employ anyone after normal retirement age, unless it states otherwise in the contract. And you have to be below normal retirement age to bring a case of unfair dismissal.
"Your employer can force you to retire at the normal retirement age. This is 65 or higher, depending on what your contract says.
There are rules about how your employer can force you to retire. These include giving you written notice of the date you're due to retire. You have a right to request to stay on beyond that date and the notice must tell you this as well. The notice should be issued between six and twelve months of the date you're due to retire.
If your employer fails to follow these rules, you can make a claim to an employment tribunal and may be awarded up to eight weeks pay �see under heading What you can do about age discrimination.
If you ask your employer to work beyond the normal retirement age, they have to consider your request but they don't have to agree."
I agree that the company has not followed proper procedures re notice and so on, and you may get up to 8 weeks pay if you take it to a tribunal.
You have already received 6 weeks PILON, so it is up to you if you wish to pursue it.
http://www.adviceguide.org.uk/nireland/life/em ployment_northern_ireland/age_discrimination_a t_work.htm#who_does_the_law_apply_to