Thanks @Sadim for the response. I am originally from the UK, so lived in the UK up until 2006 when I moved to Ireland. 2005 was when I started permanent employment but I'd previously have had a 1 year work placement in 2003 and various summer jobs before completing my degree in 2005 and starting work.
When I first moved to Ireland it was a secondment with a view that I would eventually return to the UK, so I stayed on a UK contract during that period and paid tax in the UK - although I didn't live in the UK I was paid into a UK account and payslips may have been sent to a UK address, I can't remember. The move to Ireland then became permanent in 2008 when I signed an Irish contract.
Might be clutching at straws but any hope the above might make me eligible?
Strikes me like you are exactly the case that the cheaper Class 2 contribution was designed for. The Class 2 rate was originally introduced for the self-employed but eventually was extended to UK nationals who went abroad on "temporary overseas assignment". The temporary bit seems to be irrelevant. Anyway, download a Form CF83 from the HMRC website, complete it and send it off to HMRC Newcastle.... takes a while to get a verdict from them though.